Speaking of this I decided this morning that I might need to graduate from 50x34. Spinning at 35mph on the flat using the car ahead as a target in 50-11 and couldn't really get any more speed out without crazy fast spinning.
My Diverge is on 52/36 and an 11-32 cassette. My Defy is a 50/34 on an 11-32 again and I do spin it out more. I've done a 25-30% climb in 36*32 and hardly noticed any difference to 34*32.
I still spin out 52*11 descending, but not on the flat. I would spin out 50*11 very occasionally on the flat/gradual downhill chasing on group rides/sprinting, but I don't find myself in 52*11 doing the same thing.
I spin out 50*11 quite regularly on the turbo.