Using DP since it was out.
I have encountered following bugs :
1) Random reboots. I believe firmware update will fix it.
2) Reboots on using word flow keyboard [usually when battery saver is on]. No idea why it happens , but I can reproduce it almost daily. *
3) Sometimes my right earphone gets muted. In WP8 my volume used to get stuck , and in WP8.1 the right earphone gets muted. I have tried different earphones , doesn't work , and have tried them on different phones , works. The only fix is to reboot. I wish it gets fixed with firmware update. Or maybe it's just poorly written apps like whatsapp etc which fiddle with audio.
4) Sometimes screen doesn't detect touch. Someone had posted a video about it, what you do is that you open any app ,quickly press home button and then try to swipe the start screen. It won't detect it for 2-3 trials and then work after a lag. It bugs me when I am doing some quick multitasking stuff. This is original to WP8.1. I don't think firmware update can fix it.
5) I get No service from nowhere. Toggling airplane mode twice still doesn't fix it. The only way around is to reboot.
* Seems to be fixed by WP8.1 update.