My report goes something like this for my Lumia 930.
Reboot loop with latest build, so restored to 8.1, upgraded to latest W10M build, hard reset, restored a W10M backup from day before. All apps and updates installed ok, no stuck downloads.
Seems to be more buggy than last build, for me at least.
Alarms have been ok so far, no need to cancel it twice or more when it goes off.
No emails this morning, opened Outlook, manually initiated a refresh and mail came through. Verified that it is set to collect every 15 mins, so not sure why it didn't collect any mail overnight.
No notifications on lock-screen for any apps, though I did get a single number appear just once, but even then it didn't have the usual icon next to it, so I'm not sure what the notification was actually for. Can provide screenshot of this if anyone is interested.
Some live tiles don't seem to be working, missed calls, texts and Outlook tiles ok, but others such as Windows Central, Amazing Weather (see text below) not working.
Amazing Weather - gets to splash screen then comes up with message saying "Error occurred". Have screenshot of this too. Obviously live-tile does not work either as mentioned above.
I think there are a couple more things that I can't think of right now, but will edit this post later if I remember.
Overall it's ok still, performance pretty good, nice n smooth, battery life about the same as it was on 8.1 Being on the insider program means that I'm not expecting perfection, but I hope for Microsoft's sake that the new Lumia 950's don't suffer these issues.