Nothing really. For someone comfortable with the level of intrusion in Win 8, Win 10 won't bring you too much extra joy or sorrow. I personally am fine in Win 7, without the useless store, tiles, metro apps and whatnot from Win 8, but that's just me. Being a free upgrade, people will migrate without thinking, and us developers will have to satisfy their needs for apps. More work for us! Yupeeeeee!