Got the same problem on my 925. When i first installed the preview from 8.1 I had overall terrible performance and battery drain, then did a factory reset. All issues improved, and 10 ran great, that was about a week ago. Today however I'm back to the same old quick-drain problems, and charging happens real slow too (<10%/hr). Had my phone in my lap when driving today and noticed it was running pretty hot while locked/asleep. drained 30% in just over an hour.
I'm probably gonna just have to keep doing resets until the next build comes