I've had a couple of alloy frame 1911s and have shot moderate amounts of +P ammo through them without any appreciable wear. Like any other aluminum guns, a lot of +P ammo will probably wear faster but you'll probably shoot all your stash long before you wear out your frame.
I don't use +p, especially in an alloy frame. I just don't see the need for range work. A steady diet of +P is not recommended by any of the manufacturers that I am aware of. It is okay for carry, and of course the occaisional test at the range.
I don't personally see the need to run +p ammo. I guess, the theory of a higher velocity impact is more effective... but what really drew me away from using +p rounds was the fact that I could go to the range and put in all kinds of practice with FMJ, but then when I load up a mag of SD rounds that I intended for carry, it would handle like a different animal. I have been using Federal Hydroshocks for the last couple months, and I really like their predictable recoil.