Pros: Comfortable, stable with good feel; true fit/sizing; good grip; waterproof.
Cons: Could be lighter, sole could be thinner (more like a true minimalist shoe); styling probably too contemporary for traditionalists.
I've got 4 rounds and 3-4 range/practice green sessions on a pair of the charcoal/black mesh spikeless Project M shoes. First couple rounds were on cold (50's* F), dewy mornings, last few have been hot (low 90's* F), dry afternoons. I'll qualify my opinion by saying I'm a big fan of minimalist shoes in general and they're almost the only shoes I wear - I own (and love) several pairs of Vibram Five Fingers (VFF) and a pair of Merrell Barefoots. A big part of my purchase decision for the M Projects was to find a golf shoe that gave me a similar minimalist feel.
First off, while the M Project does have very minimal heel drop and gives you the 'close to the ground' feeling, the sole doesn't feel like a barefoot shoe in the sense of VFFs - it's definitely not as thin, soft or pliable. The toe box isn't as wide as my Merrell Barefoots (and doesn't have the accompanying "clown shoe" look either), but it does feel roomy (but not sloppy) in the toes and ball of the foot. While traditionalists may hate the look, the shoe looks sleeker/thinner than it feels, even on my size 13 feet. The comments I've gotten about the looks of the shoe from friends I've golfed with have all been favorable. I'd say the most different/non-traditional thing about the looks is the stitching pattern, but I don't find it objectionable.
Sizing, at least for me, runs right in line with all my other shoes - the 13 fits like a 13 in any other shoe I wear. Comfort-wise, they're very comfortable right out of the box with no break-in. My other golf shoes are an old pair of FootJoy saddle shoes and a pair of Oakley Ripcords, and the M Project is more comfortable than either of them. It's not a feather-light shoe (around 14 oz. IIRC), but it certainly doesn't feel heavy on the feet either.
I've had no issues with grip, even on the wet/dewy mornings. They claim to be waterproof and while I haven't gone pond wading, my feet stayed completely dry while tromping through tall, wet grass/weeds tracking down errant shots. I experienced no slippage walking up/down hills or during golf shots. The spiked (nubbed, actually) sole wraps partway up the side of the shoe on the inside toe edge of the right foot and the outside toe edge of the left foot, presumably mimicking weight shift during the swing. It wraps partially up both the inside and the outside in the heel area. The soles offer very good traction and while they don't transfer the same amount of feel as a conventional minimalist/barefoot shoe, they do offer more tactile feedback than a traditional thick-soled golf shoe. As far as stability goes, I feel like I can use my feet more ('feeling' weight transfer, pronation/supination) than a traditional golf shoe, but they don't feel like they sacrifice any stability as a tradeoff. Personally I'd like the sole to be even thinner/more pliable, but FootJoy's design rationale was apparently that they didn't think it would transfer over as well to golf as it does for running/training shoes (judging from what I read in one of the intro/preview articles).
The mesh upper breathes well. My feet didn't feel unduly cold during the cold morning rounds, but I've definitely noticed a difference the last couple days in our 90*+ desert temps...the airflow is very welcome in helping keep my feet cool.
Overall - if you're looking for a comfortable minimalist-type golf shoe and you can get past the non-traditional look, the M Project is worth considering.
As a postscript: I like these shoes well enough that I bought a second pair (spikeless, white/white leather).