Here is an article that gives a quick comparison of a G11 and a Micro 4/3 P&S:
http://www.luminous-landscape.com/reviews/cameras/g11.shtml
The G11 was at ISO 640, not at it's best, but at that ISO the u4/3 is easily better.
None of the u4/3 P&S models have an optical viewfinder which is why I went with the G11 but it sure would be nice to have that larger sensor! Maybe one day some manufacturer will make a u4/3 P&S with a real viewfinder!