wow who is going to buy your used D3000 for 550? You can walk into a Best Buy and get a brand new one for 500
I did buy the D3000 less then a month ago, and I have to think of tax and all that too, so that sounds right. And the camera has only been taken out twice.
No offense, but it doesn't matter at all what you spent for it...what matters is what they sell for at the time you try to sell. Just because you overpaid (sounds like you did) doesn't mean you will get that back selling used unless you find somebody that doesn't know any better (which it sounds like you had).
Nates have a very very good idea for you to upgrade to D5000! I don't think upgrading to t1i and paying $$ would be good, but unless you go T2i
When I bought my camera at Samy's I ask them if the D5000 was worth an extra $200 and they said that the only thing is the extra 2 MP and the video feature and I already have an HD video camercorder at home.
They lied. 2mp difference is probably the smallest reason for upgrading. The D5000 uses a completely different....tons better sensor...same sensor as in the D90, D300, and D300s. High iso performance blows away the D3000 meaning in lower light, you can shoot nicer photos without having to use a flash, 11 point AF, faster frames (more frames per second) for sequences, plus many other things. The sensor upgrade alone (not mp) is worth $200.
I just ordered me a D5000. D3000 wasn't even a consideration...oh and I spent $509 versus the $550 you'd want out of your D3000. Sorry if that seems harsh, but my point is that it doesn't matter what you spent on something...I saw a D3000 kit at staples yesterday for less than $500 brand new.