to clarify: Win 10 will launch on July 29th globally.
to clarify #2: Win 10 is now on consumer build phase. I know this because I'm an insider myself. Latest build is quite polished and the issues are minimal.
I exported my VN collection to my win 10 partition and so far 100% of them are working. Here's the list:
* Chaos Head - flawless
* Da Capo - Flawless
* Da Capo 2 - Flawless + better performance than on 8
* ef the first tale - Flawless + audio no longer gives problems
* ef the latter tale - Flawless
* Fate Stay Night - Flawless
* Go Go Nippon! - Flawless
* Muv Luv (Series) - Flawless
* I/0 - Flawless
* Kanon - Flawless
* Clannad - Flawless
* Air - Needs running as admin
* Ever 17 - Needs running in compat mode for win 7
* Little Busters - Flawless
* Little Busters EX/ME - Flawless
* Da Capo 3 - Flawless
* Koisuru Nasu Love Resort - Flawless
* To Heart2 - Needs running in compat mode for win 7
* Hoshisora e kakaru Hashi - Flawless
* Noble Works - Flawless
* Majikoi - Flawless
* Majikoi S - Flawless
* Majikoi A-1 - Flawless
* Hoshimemo - Flawless
* Hoshimemo EH - Same issues as other OS's (requires changing time zone to JP) fast fix = AlphaROMdiE
* Osadai - Flawless, (no longer needs win8 patch)
* Osadai FD - Flawless
* Rewrite - Flawless
* Harvest festa - Flawless
* Shuffle! - Flawless
* Really! Really? - Flawless
* Imouto Paradise - Flawless + better performance than on 8
* Boob wars (series) - Flawless + better performance than on 8
* Princess evangile - Flawless + better performance than on 8
* Yu-No - Flawless
* Duel Savior - Requires running in compat mode win xp
* Come see me tonight (series) - flawless
* Sharin no Kuni - NoDVD fix no longer works, requires ISO to be mounted when playing
* Sharin no Kuni FD - Same as above
* Dengeki Stryker - Flawless
* Snow Sakura - Flawless
* Stein's Gate - Flawless
* Grisaia (series) - Flawless + better performance than on 8
This is my personal collection, there may be more VN's that are compatible but I will add them when I test them again for core release of win 10.