I can afford a M7 without selling my MP but I don't want to have camera that I don't use. Not when it is a MP.
If you can afford the M7 without selling the MP, then buy it and see how you like it. If you choose to sell one or the other, shouldn't have any problems. Especially the MP.
The MP made me think about lighting and I can usually come close to picking the right settings. It's easy to over or underexpose based on what I know is a backlit or dark scene and all that (easier to it with the aperture ring than say dialing in exposure compensation on the M7)
The M7, for me, IS faster to use. The meter is fairly accurate, but I don't find myself looking at the shutter speed it's chosen so sometimes I'm off. Especially when the shutter speed is 1/8th of a second and I'm not that tripod-like steady to pull off a crisp shot. So, the M7 has made me a little lazier, but now I take photos like I have for years, with AE.
My course... bought an MP and really liked it, then bought an R4A to use with a 21mm lens. Didn't really like 21mm angle of view so sold the lens and tried to sell the body. Couldn't sell the body so picked up a 25mm lens. (I know how crazy this all is!) Really like the AE and got an M7 .85x. Have seriously considered selling the MP. Until I took some photos of it and there is something about the look of the damn thing that makes me want to keep it!
But if the price of MPs continues to go up, I'll probably part with it, buy a NEX-7 and have a digital M that costs 6 times less than an M9 and use that for digital work.