Hi...I bought a used D3000 as I wanted a smaller body at times. I found that I use the D3000 just as often as my D300S. I love it..it has great focus and features and can handle the vast majority of my needs. The only limitation with the camera is the lens it comes with as it is a relatively small zoom.
I use mine primarily with the 18-105, or 18-200 and it works very well. For a compact "almost" pocket size version I put the 35mm DX on it. I have no complaints and think this camera is great as a entry level with many built in settings for various scenes...
However I would have to recommend to probably buy the body only and share your existing lenses with your other cameras. And one final note is that there are numerous lenses that the AF feature will not work based on the D3000 does not have a built in AF motor. So check compatibility before you buy if you want the AF feature....
Lastly as I have big hands I purchased a grip for my D3000 off eBay for $49...as the D3000 is a very compact body I find that I have to hold it with my first two fingers only. This is fine unless I have my 18-200 lens on it then it feels a little unsteady. This does not improve the fps, but will substantially improve you ability to grip and hold the camera and also your battery life as like most grips it will hold a second battery. I do not have the grip yet as it is coming from China or similiar..so I can post again later after I have had a chance to use it.
I will note that I shot (without a flash) 1237 pictures in one day on AF and the battery still showed one bar left on battery meter...that is with just the one battery it came with..so it will work well for all day shoots...
I have heard that (even read) that D3000 is the most horrible camera that has been produced by Nikon.