Yes, I also still have the problem with my iPad 4 (the iPad is not even two years old).
The reboot loop occurred the first time about three to four weeks ago (update to iOS 8.3 was way earlier). I had the iPad running (it displayed a photo) for about one hour, then I closed the smart cover. When I opened it, the reboot loop started. I wasn't able to fix it with iTunes (tried everything from setting it up from backup to setting it up as a new device). At first I thought the crashes / reboots were triggered by the screen rotation, but then it just started crashing randomly (sometimes it is okay for 5 - 10 minutes, then it only works for a couple of seconds or starts a new reboot while already rebooting). The update to iOS 8.4 didn't help a bit.
What confuses me is this: two times now I have used the music app on the ipad and basically had it in ipod mode: I played the music both via the speakers and the earphones, with the smart cover closed --> therefore "no display" in use. And the ipad ran smoothly without crashes or reboots for over an hour until I stopped the music - possibly even longer. I also paused the songs several times via the earphone remote - no issue whatsoever.
Does anyone have any ideas? How do I best notify Apple about this problem?
Thanks!