I've been running this on my daily use 920 since it was released, and other than a few minor glitches, have been happy with it.
But in the past 2 days, things have gone completely to hell. My phone has frozen up numerous times, gotten horribly laggy, apps spontaneous close all by themselves (Cortana, FB beta, Photos, Messaging, very core apps), keyboard won't come up at times, etc. It has bordered on unusable. I've done a soft reset, but no hard reset yet. I haven't installed any new apps.
The only thing I've done differently is that I haven't been as anal about closing out apps completely using the task manager. There's a thread here about suspended apps making more efficient use of RAM. I don't know if this is related or not.
Has anyone else seen theirs start to misbehave after running fine for some weeks? I'll hard reset if it doesn't get better, but that's getting really old.