This is all very well, but something like a GF-1 or EP-1 costs double the price of a G11 or S90. Plus, once you fit those cameras with a zoom lens that gives it a similar range to the lens on the G11 or S90, it does not seem that small any more does it? In my mind, a GF-1 or EP-1 with the pancake lens, is not that much smaller than a small DSLR with a 24 , 28, or 35mm prime lens. These micro 4/3 cameras are nice developments, but for many photographers, something like a G11, or LX3, or S90, or GRD, have good enough quality and features, at much less cost.
As somebody else already mentioned above, carrying a DSLR with a prime lens is actually not that dificult, is it? I can carry my 5D MKII (with grip) plus a 50mm lens in a shoulder bag, no problem. To each its own, and it is wonderful to have so many choices!