Outside getting used to the start menu and readjusting all the settings back to what I like, I haven't had any real problems with Windows 10. Except maybe the scroll bar that appears when using my laptop's touchpad occasionally locks up. Doesn't really affect anything, but annoying.
I've noticed that after waking my computer from hibernation, the Start-menu appears to die. Clicking it, or hitting the Windows-button, does nothing.
I solved this issue by turning off auto-hibernation. Silly computer, don't sleep, you need to dance for your master! Dance!