If you're stuttering only at the beginning of maps, check your universal offset settings in osu!, when too high/low it can cause that stutter. The issue i believe this thread is about is an issue where the game will constantly stutter throughout playing, and it's like the map/song get rewinded for a second when it does it.
For an update on my previous comment; My driver needed updating which has fixed the issue for me, so I think turning off SuperFetch (and disabling it to stop it from automatically starting again next time you turn the PC on) seems to be a fix, it pre-loads apps that you use often, so if you play osu! everyday it will set it on preload to "load faster", along with any other apps you use alot. Wondering if it can be having a conflict somewhere with the game?
For an update on my previous comment; My driver needed updating which has fixed the issue for me, so I think turning off SuperFetch (and disabling it to stop it from automatically starting again next time you turn the PC on) seems to be a fix, it pre-loads apps that you use often, so if you play osu! everyday it will set it on preload to "load faster", along with any other apps you use alot. Wondering if it can be having a conflict somewhere with the game?