[lisaly]

Any one of those cameras has the capability to take wonderful photos, so what I'm going to say next is what my preference or recommendation would be based on a number of factors that I think are important in a camera for me. I use the Nikon D300, and it was replaced by the Nikon D300S. I love it, and feel no need to upgrade from the model, even though there are nice improvements to the camera with the D300S. Technology keeps improving, and a camera's ability to capture images in low light has improved substantially. With lower light ability, cameras can take pictures with less grain or "noise" (in digital terms), and that, to me, is important. As much as I love my camera, if I were to buy a camera when both the D300 and the D300S were both available, I would have gone with the D300S, even though the savings on the D300 were substantial at the time. I think the new technology is worth the difference, not because I need to have the newest technology, but because I like the improvements that I can see as a result of it. When I buy a camera, however, I don't want to upgrade it every couple of years. My camera doesn't have video, and the D300S does. It's not important to me, but I think having the video is very nice. I like the magnesium alloy body of the D300 and D300S, which makes it more rugged, they both have great weatherproofing. You really don't have to worry about it in inclement weather, which is great. I probably wouldn't recommend the D300S, however, mostly because it's a bit of overkill unless you are very seriously into photography. I've been using SLRs for about 35 years, many of which are pro and semipro models. I still have not completely figured out the D300. The camera is optimized for someone who is more advanced, so it doesn't have any of the scene modes which many people like. The camera is also fairly heavy. It sits really nicely in my hands, though, and I like the balance and weight of the camera. If you aren't used to using a camera like this, you may not like it. I have small hands, and I'm only 5'2', and the camera is fine for me, but many people find it too heavy. I think it would be nice to have one smaller also, but I use some heavy lenses, so the weight is nicely balanced with those lenses.

I also love the D90, and it has a JPEG engine that is more optimized for someone that doesn't want to play around with postprocessing than the D300S. Straight out of camera using jpeg, the photos are usually nicer unless you seriously know what you are doing. I wouldn't put myself in that category, even though I have a lot of experience and am very serious about photography. It's lighter than the D300S and smaller, but not by a huge amount. It is made of polycarbonate, but it is a strong and nice body. I highly recommend that camera. I do think the camera will be out of the lineup in the not too distant future. That wouldn't bother me, but again, I would probably go with one using newer technology unless price was a big factor for me. The D7000 is a great camera, and if the price is not out of your price range of what you want to spend, I probably would go with that one. The D90 has video, but it was Nikon's first camera to incorporate video. There are nice improvements to the video and the camera is using the Nikon Expeed 2 engine for stills instead of Expeed 1. I am certain that you would love the D90, but I like some of what the D7000 has in it. It has a 100% viewfinder, which is important to me, and it also has two cards SD card slots, which is great to have instead of one. It is incorporating some of the improvements in the pro Nikons. I don't think it's necessary to get the D7000 over the D90, but if I were chosing, I'd go with the D7000 today. That said, I'd love the D90 also. The person that is most known for his insight about Nikon is Thom Hogan, and his website byThom.com is great if you are interested in anything Nikon. I highly recommend his e-books instead of the camera manual regardless of what camera you buy. He loves Nikon but is also critical of them, so when he irecommends something, I take him more seriously than most other reviewers. He wrote this on his website:

2010 Nikon News and Comments by Thom Hogan

"Sept 24 (news and commentary)--

I'll just state up front that I think that the D7000 is the most important camera Nikon has introduced for consumers since the D70 (and perhaps the D700 if you consider it a "consumer" camera; it's certainly a camera that a lot of consumers purchase). The 7 numbers have been important to Nikon in the digital generation. The D70 was what got them significant consumer momentum. The D700 stole the full frame momentum from other companies. The D7000 will…well, it should turn out to be right in the sweet spot of where the advanced amateur wants to be. The only thing the D7000 doesn't have that the target audience might (think they) want is full frame.
In case you missed the announcement details, the D7000 is a 16mp DX camera, 6 fps, 100% viewfinder, more metal and sealed than the D90, and has a number of features previously found only on the pro bodies (exposure measuring with older manual focus lenses, for instance). The D7000 also gets 39-point autofocus, double the pixels in the metering sensor, twin SD card slots, 1080P/24 video, and a new shutter tested to 150k activations, amongst other things. The D7000 is not the D90 replacement according to Nikon, but will slot in between the D90 and D300s in the lineup. That last is a wee bit of marketing chicanery: Nikon has a sufficient inventory of D90's still and has continued to make them as the D7000 started production. Still, I have no doubt that the D90 will be out of the lineup within a year, probably less. The D90 will likely be featured heavily in those weekly deals that Nikon does pre-Christmas, and once production shuts down and those cameras are gone, the D90 will be history."

If you want to read about any of these cameras, I would recommend reading his reviews to help you decide.
Nikon D90 Review by Thom Hogan

I read Ken Rockwell when I was first reading about digital cameras. I didn't know anything about digital, and that was only about 4 years ago. Since I've read a great deal since then, I've realized that there is so much misinformation that he spouts because he is so highly opinionated, and he changes his tune often. He has a lot of good information for an amateur, but because there is so much misinformation, I'd stay away from his recommendations unless you check into them a great deal. He is not well regarded by those who are knowledgeable in photography. I probably would have gotten a digital camera before I did if I had not read his website. Although technology is constantly changing and improvements are seen, it does not make your camera obsolete, and there is no need to keep upgrading your camera. Although I like a lot of the changes that I am seeing, I am thrilled with my outdated D300. When I do upgrade, it will be because I want to get an FX sensor instead of a DX sensor, but that's not something I'd recommend for most people. Since I've been using Nikons for over 20 years, a lot of the lenses I own can be used on my DX camera, but they are more optimized on an FX camera. I'm used to a full frame instead of a 1.5 sensor and I like how an FX sensor has less depth of field. Otherwise, I recommend DX camera, which you are looking at.

The other cameras are excellent, but they don't have a motor in the camera. You can use lenses that don't have motors in them, but they don't have autofocusing ability. There are plenty of lenses with motors in them, but it limits you. You can't use Nikon's 50mm 1.8 lens, which is a great lens for about $100. If price is a factor, they are great cameras that I wouldn't hesitate to buy. I just like the ability to use Nikon's extensive lens lineup and having the autofocus lenses having that ability. If you decide you like any of those cameras or want to stay in that price range, I will go over each of the cameras for you, including the pros and cons.

I tried to do this quickly until I knew more of what you were leaning toward, and I ended up writing more than you're probably interested in. I'd be happy to help you further once you hold each of these cameras in your hand and see what you like. The D3100 is a lot smaller than the D90, D7000, or D300S, and you might like that. You can't go wrong with any camera you choose. I like having the autofocus motor in the camera and not having to get all lenses that have motors in them. If size was a factor for me and I wanted a smaller camera, I wouldn't hesitate to get one of them. It's really what you like, and they will all take excellent photos. If you decide to go that route, let me know and I'll help you further comparing them. I'd be happy to talk to you about all of this, and I can PM you my cell number if you want to speak to me. Whatever you choose, I think you will love it. Canon has great cameras too and a more extensive lens lineup, but I like the quality control of Nikon and the fact that it has a lot of great kit lenses. Canon saves its better technology for its higher end cameras. Nikon filters down the higher end technology into its consumer line. They both take great photos, but I prefer the use of Nikons to Canons.