1) First the nasty one: No background images gets set and you are back to default wallpaper-less background and obviously without “Translucent tiles”
2) Outlook can’t send mails and always shows some server error.
3) The Action Center scrolling is not smooth and there are noticeable lags while expanding and collapsing the quick action buttons.
4) Internet explorer web page rendering is fast but the scrolling is worse than what you may have experienced on GDR1 build
5) Images transferred to device via Bluetooth disappear after “successful completion” of transfer.
6) Settings crash, especially the personalization settings crash sometimes
And there can be many more. Do let us know what you have seen. I have posted some of the bugs using the “Windows feedback” app and hope you would also be doing the same. You can also use a shortcut to give feedback from any of the app.