If the phone didn't have integration then I would consider it, but there is too much feature overlap.
Same with Twitter. I don't actually even use a twitter client at all because on the occasion of having to do stuff that the OS can't, I just use MetroTwit.
I will pay a maximun of 1.99 bucks for a fully feature, beautiful, fast, metro Facebook app. ( And not the lazy way of just black/white background, I want pretty pictures )