the 550D is no doubt tempting man...i want the high ISO performance! but til i get a hands-on with this camera its hard to tell if its worth switching to from 50D.
I don't think it will be worth it. Why would you want a smaller, slower camera? If you wanna switch, then switch to 7D or wait for 60D, if it ever comes out. Otherwise, I suggest you keep the 50D. It's like you own a mercedes e-class, and then change to the c-class just because the new model c-class has more features.