I've gone back to 8.0. After the last update for 8.1 my 925 went wonky :-o Hard reset didn't work. Phone would just ------- stop dead in it's track occasionally. Nothing. Like the battery wasn't even installed lol. At first I thought my phone was bricked. Last time it happened, my phone was absolutely useless for a good 10 mins. Out of the blue it would just come back on .... strange. No problems being back on 8.0 so far (4 days). I miss 8.1 though :-( I'm more anxious for the Cyan + 8.1 release now.
I think I'll purchase the 635 to replace my 521 when it becomes available haha. I'll keep the 925. Use the 625 as a work phone (I work in a machine shop)