After updated to w10 pre
1. The background program do not close - no program closes with 'back' key. It keeps the tiles open, program running!
2. The battery is drained heavily
3. every program needs closing multiple times, at least three times
4. my L1320 getting heated which was not the case with w8.1 update2
5. browsing for files, say photos or media on SD card has become extremely slow, even crashing some times.
6. every program is starting very slow.
7. Net connection over wifi has become much much better.
8. USB connection is also very fast but blue tooth connection with w10 is fine, with w8 it fails authentication.
9. sensitivity of the screen needed readjustment to at least medium for normal operation,
--- till date this is the status of my lumia1320. Though getting frustrated but not yet going back. Want to test for some more days b4 going back, if necessary at all. Waiting for another update very very soon on w10 pre!