Canon XSi vs. Olympus E-620

I am new to DSLRs and have been looking at the Canon XSi and T1i as these are in my budget. I have heard that Canon is the way to go but don't totally know why. A new camera shop has me now looking at the Olympus E-620 saying I can get so much more for the money. Is this true? What about IS in the camera body and not the lens? Any feedback is much appreciated as I'm very green and looking for direction.

Thanks!