sharkyy, it's basically a Canon 10D with a few less features.
Same sensor, same processor.
So I can assure you, speed and optics will be excellent. The only real drawback vs. the 10D I know of is it shoots less frames per second and has a smaller buffer. But if I never had the 10D, I never would have missed it.
Also I know in the SLR world a 2x optical magnifier (i.e., teleconverter) is pretty well known for effecting picture quality rather negatively. No way in hell I would spend $500 on one of those, they're only $250 for a top-of-the-line SLR model. Definitely wait and get the Digital Rebel, you won't be disappointed with where your extra $300 went.
BTW, I completely expect the included lens to suck, but for $100 it's probably good enough to have around.
T