I usually buy my DSLRs right AFTER their manufacturer has come out with the replacement model. That's when they are their best value. The new model will usually cost around 30-40% more than the old one, but only actually be around 10-20% better.

That's why I got a Nikon D80, after the Nikon D90 came out. The D80 dropped in price from $900 to $500 over the past year, and now the D90 body costs $900. It's a slightly better camera, but it's not anywhere near as much better as the price differential would imply.