The great thing about the GR Digital range is that Ricoh give you a hell of a lot of control over the picture taking process, more than most compact cameras do. Sure, it's a small sensor so you get noise at higher ISOs, and it's a wide angle lens so you need to get closer to your subject, but within its minor limitations it's a fine picture-taking machine for the reasonably serious photographer.
It's compact and pocketable, more pocketable than any micro four thirds camera (I can just about fit an Olympus Pen E-P1 with 17mm pancake lens in my pocket, but it's not comfortable), feels sturdy and well made.
As far as Alan Firminger's remarks, I think most of the delay with compact cameras comes from autofocus. The GRD can be focused manually - also they have a fixed focus modes, where you can set infinity focus or 'snap shot' focus (a few yards away) reducing shutter lag to practically nothing.
The only problem I've ever had with my original GRD is the long time it takes to write RAW files. Ricoh have completely fixed that, it seems. If my old GRD gave up the ghost, I'd seriously upgrade.