I have to take issue, at least partially, with John's post, too.
Cameras like the GH3 are close in size to the smallest DSLRs, but in terms of build-quality, features and many performance areas they're more competitive with mid-range and better DSLRS (though certainly not pro-level ones). A GH3 may be the same size as an EOS Rebel, but that camera is more realistically compared to something like the G5, which is smaller still. Compare a GH3 to a 7D, or 70D, and it's quite a bit smaller. Add a couple of f/2.8 zooms to each system, and the difference is magnified.
For what it offers, a GH3 kit is still quite compact.