In-body IS matters to some, and not to others. If it does to you (it does to me!) then Canon & Nikon are out of question.

If you want Olympus then i'd suggest you to wait for the new E620. Smallish OVF and 3 point AF on the E520 put me off.

Right now, the best entry level bodies come from Sony & Pentax IMHO. I picked up my Sony a few months ago because the system has AF Zeiss lenses, and I have the option to go full-frame in future, if photography grows on me.

Hope that helps.