GMCloud: Ya that kinda blows that this just came out right after you got your XT.
I still don't think the improvements are that significant to justify upgrading. Unless you plan on blowing up your pictures to huge poster sizes, which not many people do, or you crop your pictures like a manic, the 8MP should be more then enough for you. The bigger LCD screen is nice, but I find mine fine. I think the self cleaning feature is really cool, but I've had my camera, and two lenses and haven't had a need to clean the sensor, no visible dust on my images. I think as long as your careful with where and how you mount them, as well as storage you should be OK. The improvements are nic,e and the price is right if your looking to get one, but not worth the price jump from a 350D IMO. Heck, I see people with the original Digital Rebel (6.3 MP) turn out some incredibly beautiful shots. Remember your images rely more on your glass then the body.
I'm really hoping this new camera combined with the 30D lowers the 20D significantly, so I can get one pretty cheap, although it will probably be some time.
I'm also glad you enjoy your 28-135mm, even though you had to go through 2 other copies. I honestly would have gotten a new lens if I had that much trouble. It's a nice lens though if your on a budget and only want one lens mounted to your body. I've been having a lot fun with my new Tamron 17-50mm f/2.8 even though I haven't taken it out in a while. Compared to my 28-135mm it's SOO much more wider even though it's only 11mm.