I've recently upgraded to FF from crop, and in the process converted most zooms over to primes. Loving the incredible sharpness, quality, and DoF/bokeh. Driving reason behind it, besides feeding an obsession, was for family portraits. Also keen on macro, landscapes, and travel photos, but feel my previous equipment handled that all fine. I could have made do, but the other things that tipped me toward the 5DII was the high ISO performance and also the video. New baby, want to capture video as well.
Current lineup is 5DII, 35L, 85LII, 135L, 180L, 17-40L, MP-E65, 100-400L.
5DII - couldn't be happier with it.
All of the lenses are wonderful. Primes sharp. L series build quality.
85LII is a beast of a lens, so big. Just looks plain sexy. When I first took the lenscap off I heard this whistling sound and didn't know what it was. Then I realised it was the lens sucking in the light faster than anything you can imagine. Ok, I exaggerate
AF is a little slow, but not as bad as I thought it would be.
135L - one of Canon's finest. Sharp, fast AF.
180L - wife has the Sigma 105, so wanted more reach. Have the Sigma 150, no complaints about it at all, but the WD of the 180L is just a little more.
17-40L - contemplated the 16-35LII but couldn't justify the extra money. Situations I use the 17-40 aren't really low-light, so the f/4 isn't an issue. If I am indoors, the 35L is typically plenty wide on FF and fast enough.
Must say I'm very happy with going primes. Aside from the above-mentioned, they really force you to think about the shot more, because you don't have the flexibility of zooming in and out. I think that's a good thing.