Hmmm....not particularly crazy about the black-out on the shutter speed dial. Particularly if I'm working in low light, I wouldn't want to have to squint to figure out what shutter speed I'm using (so I'm looking at that aspect from a purely functional point of view). The other thing that occurs to me is that if this was your plan all along, why bother spending the extra money getting the P model? Guess the sapphire crystal does add something, but you likely could have accomplished the blackout look with a standard M9, and save yourself $1000 in the process. Just a personal viewpoint, mind you!
Like you, I did buy the grip, and I love it. It definitely changes the way that you hold the camera, and gives a more 'secure' feeling when carrying/holding it. Definitely recommended.
As well, I bought a half case for my M9 (a black Zhou w/red stitching). It's a very nice case for the money (about $70), but changing memory cards and batteries on-the-go can be a bit of a pain, and now that I use the M9 grip, find the half case unnecessary. Of course, now that I don't use a case there are likely to be more scratches and marks on the baseplate, but I suppose that's all part of the experience of owning and using a camera.