Olympus E-P3 vs. $500 Compacts

theoretically that would be an option if you know beforehand what situation you are going to encounter.

Judging from past shots, a 2.5/14mm on m43 would cover possibly half of my walkaround shots, and such a camera can be very compact (and probably a lot better in good light). But I would miss the tele end / DOF control in other situations. I don't want to carry both a camera with WA prime and an extra lens, 'just in case'. Also, sometimes a bright standard prime (that I don't need to stop down for good corners) would be very nice, but in reality I use standard focal length for just a small percentage of my shots. So it would stay at home all the time, probably ...

If I have to plan ahead for what equipment I am going to carry, I would probably take my DSLR for even better quality and ergonomics. Extra options on the compact or m43, like high quality EVF and flip-LCD, can bring additional advantages, so those influence the decision as well. But until now, all options with a flip-LCD are too big or otherwise not my taste ...