The burst is definately much better than the 350D, as well as the noise at high ISOs I believe.
I got my 20D body for $1400 about a year ago.  I have Canon 50mm f/1.8 II and 24mm f/1.4L lenses for it.  One lens cost 13 times as much as the other, but the cheaper 50mm is so sharp, it's definately worth picking up.  I also have a Speedlite 420EX, which I rarely use unless I have to.