Search has been an incredibly finnicky experience. I had to use PowerShell commands to correctly search the contents of files in a folder, checking the options in Explorer did nothing to accomplish this. "No results found", yet I run the script and oh look 25 project files contain this string.
The Start Menu has constantly been slow for me, and often times I can't search and/or click anything. This is incredibly frustrating.
Having to disable so many features out of the box is annoying, and the amount of effort to disable telemetry without some helping script is absurd. I'm not sure I even got everything the first time since it seemed like more registry values needing modification were being discovered continuously.
Any large update takes a substantial chunk of time and multiple reboots. I sat in front of my computer as it updated for at least two hours with 4 reboots. I didn't even get to use it. This was last week. On top of that it restarted while I was grabbing a snack. I didn't get to use it again before bed. This is hardly acceptable when I may actually NEED to use it.
Still have gotten blue screens of :) death on multiple computers, work and personal. They're happy now at least, but doesn't change the fact I lost some work.
Inconsistency between Windows programs is also frustrating. There's at least 3 different design styles, maybe more, than go into the default Windows programs. Difference in font, spacing, window design, icon design, alerts, etc. that really show fragmentation even still after 8, 8.1, and still on 10 trying to modernize their OS.
These are a few things that I've still found wrong with Windows 10. Just about all of these in the last week, I'm not trying to look much farther back.