I have previously installed windows 10 mobile preview up to build 10166 on Fast ringer, all three times I had to return to WP8 to make use of my phone. I?ve experienced laggings and apps not working as they should. I know all these builds are still on beta but from what I can see some are happy to run WP10 previews on their phones without having any major issues. I?m starting to think it?s the 925 that has the issue. Is there anyone that is running WP10 preview without major issues? (e.g. after starting or waking the phone, the start screen loads up for about 2-4 min before you can see it)