Minor issues that I've come across after a full day of use include: Xbox game streaming largest/crashing on 75mbps network, Xbox app consistently not launching when in tablet mode, metro apps (is this still the term?) not downloading, store crashing, surface pen stopped registering (restart seems to have fixed it), and tiles not wanting to resize. Again, minor things, but just some little annoyances.
An oddity for me is when I choose to open a PDF in Internet Explorer (still using because my nursing course uses Silverlight) it opens the PDF in Edge instead of the PDF app. At first, I kept thinking the app was crashing because you'd see the loading bar, but nothing would pop up. Wasn't until I started minimizing things I saw it. Also, the Xbox app making you use extra apps to do things it shows inside the app seems... unfinished I guess is the best way to say it politely (expected, but maybe take out the feature like "customize avatar" if it's going to make you download another app which then proceeds to give an error message lol).
All in all I'm still loving the upgrade. Now lets get a dark theme for Groove or a system wide auto day/night theme where based on the time of day it chooses between light and dark theme.