In my opinion is that I would stay with a d5000 . A d90 have mostly similar specs as a d5000 (according to KenRockwell) , so why spend so much for an almost similar camera ? A 50D is another choice , but when you switch to another brand , you will tend to compare . It certainly is an investment as to your personal experience with both brands . You wouldnt want to reach to a point where you compare and conclude that (example)nikon is better . Likewise , if all goes good , the 50d might just suit you like all magic . Like I said , an investment . If I were you , I live with what I have and spend the money on lens and accessories .