iTunes doesn't open, no error messages or anything, not even when executed through terminal I just updated to iTunes 12, and I when I open it, nothing happens. The icon on the Dock doesn't even bounce. When I start it in the Terminal, nothing happens either, no messages. When I open it with sudo, the application does show up in the dock with a dot, but no messages or UI.

I don't think it has anything to do with my user profile since it does not work in sudo either, it does come closer to work though, but it's a very very small difference. I have rebooted the computer, obviously.

I also tried reinstalling it, it's been stuck on "moving files to their right places" with 1 minute left for 7 hours.
"1 minute left" is the sign for "I'm doing your user stuff right now, I have no clue when it will finish, 'cos that depends on how much stuff you've got" … but if you've force-quit it, you broke it &amp; will have to start over.  

There is similar confusion at OS updates, the "doing your user stuff" part apparently cannot be predicted anywhere near as well as the initial processing/update, so you get a "1 minute" that can take hours. Patience is a virtue; in fact patience should be directly proportional to the time since your last solid backup.

I'd clear the saved state for starters &amp; see how that goes …
~/Library/Saved Application State/com.apple.iTunes.savedState