Pita is very capable of hurting the ferrets as you've seen in other threads about her kitten maiming incident(
http://www.yorkietalk.com/forums/showthread.php?t=29349)
but the ferrets have lots of places to hide, plus they put her in her place. So she plays with them just fine.
I don't know about anyone else but ferrets
do smell, they have their own musky odor which isn't bad but if you don't clean their cage very regularly, their poop (and they poop ALOT) is very stinky.
I love them tho, mine stay outside in a screened area, they are so funny and fun to play with. Just for the record they are not rodents, they are in the weasel/mongoose family, they are not nocturnal. Ferrets also like alot of out of cage exercise and attention. They are definitely not for everyone and each one has their own distinct personality. If they are mishandled when they are small they can become mean and nippy so I don't recommend them for little kids.
Mine love the tunnels I have around for them i make them out of the plumbing pipe you buy for the sewage line at Home Depot and I also buy them dryer venting to run around in. They also love a feed sack or big box full of newspaper or hay or anything to nose around in.
They are soooo fun!