Kalen:
Jack Nicklaus did several L-shaped greens early in his career -- 17 at Glen Abbey is one of them, Castle Pines and Loxahatchee also had them, and probably a few others I can't remember or didn't see. However those greens were all pretty flat, so if you were stymied by the bunker in the crook of the green you just had to putt on the dogleg. (MacKenzie built a couple like that also, late in his career.) Presonally, I think the concept goes from cool to awful if you don't have a slope so you can putt around the bend in the green.
Bart:
I would try to explain my opposition to the M green more, but I guess it boils down to personal preference. I just hate a hole with a big backstop at the back of the green, and (with a few prominent exceptions) I am generally not fond of greens laid out wide and shallow to the line of play, ESPECIALLY if they are symmetrical ... I just think they look horribly unnatural. I will leave it to someone else to try and build your "M" green to prove my point.