That's what I had - then my hubby got me the D90 for Christmas, so I sold my D40. The D40 is a nice camera, very light weight, lots of features to learn about. The real thing to consider w/ the D40 is that the focus motor is *not* on board - in other words, if you want auto-focus - you have to buy "AFS" lenses vs. AF etcetera. You have to buy lenses that have the focus motor IN the lens. Of course, you can manually focus, but that may not be what you always want to do.
One of the best and cheapest lenses out there, for example, is Nikon's 50mm f1.8 - super, super lens and only about $100! But, on the D40 - it will not auto focus. So, if you wanted a prime lens in that range - you'd probably have to get a Sigma 30mm and pay about $400 for the lens. So, the lens issue was my real beef w/ the D40 - but if you aren't into a lot of lenses, it may not be an issue for you.
Here is a review:
Nikon D40 Review: 1. Introduction: Digital Photography Review