I grabbed my 925 last week and the first thing I did was update its firmware to the Black version (standard procedure). Then I installed the Developer Preview and patiently waited for all the updates to take place. Finally I did a hard reset with no backup restore, following some insights I found in the WPCentral forum.
So far I had only one issue, today: the phone simply lost all the sound, for anything. Vibration was still working, though. I just rebooted and everything came back to normal.
Regarding battery, my first cycle after the updates gave me 8 hours of use. Consider all the updates that was made (Black firmware came on charging and the 8.1 off) and a long phone call, plus some downloads and tweaks, and it's comprehensible. Now I do get more than a day with a single charge, as I'm not always using my 925.
It's still soon to assume I'll be bug free, but so far I'm very happy. If you're feeling adventurous, go for it; I assume the Lumia devices are not as problematic as the Samsung devices for this Developer Preview.