Pros:
+ Get updates regularly
+ It's a free update (if you have Windows 7, 8 or 8.1)
+ Have Cortana
+ Internet Explorer has been faster than before
+ Can play some Non-unicode games without Region change (not confirmed)
+ Less Blue Screen of Death
Cons:
+ Some sources claimed that Microsoft is using Windows 10 to get private info from consumer's PC (haven't confirmed)
+ Compatibility issues with some games (some VNs like 小女ラムネ」の起動 and ひまわり!! ‐あなただけを見つめてる crashed for unknown reasons)
+ Extremely RAM consuming for some dumb reason if using Chrome or Firefox
+ If access Windows Store, ads gonna bother you... A LOT !!!
+ No Windows Media Player (that means that you have to install manually, search on Microsoft page for more details)
To sum this up: Windows 10 is buggy as f*ck. Recommended using two Windows, in case of Windows 10 gets too buggy for you.