I switch around this time last year to OSX mostly since I want a unix system with photoshop and other apps I need for work.
1) Took me roughly 2 months to get used too it, some things where really annoying, like the keyboard being different @ vs " was a huge pain point for a developer that uses " 2104120412 times a day for strings
. But now I can't go back to anything else and I love how OSX work, still hate some of the keyboard choices but meh XD.
2) Yes. This is due to a lot of things, spaces is great I love them on linux love them on OSX, I can easily spread work out and never need too alt tab. Short cuts are awesome, every app I've used uses cmd + , for settings, cmd + w to close a window, cmd + q to quit an app etc etc. Once you learn the hotkeys your life becomes so much better.
3) You have access to VLC so it does everything the windows version does, I also use MPlayerX which has no issues with file types but still lacks features like playlist which is key on a Friday night when me and the misses catch up on the weeks shows. I also watch a lot of Anime with 10bit etc etc without any issue.
Dont use Office for anything.