Nothing particularly on my mind yet. Other users, including myself, have been working on it, like testing driver compatibility, old program compatible, some games to get rough idea if the OS is good for games. It looks like a very capable OS on desktop environment, apart from Metro, which can be turned off so problem fixed.
But I haven't seen someone test it on touch screen device and run on battery to give us a rough idea on battery. I mean, this OS is aimed at tablet and phones so we would expect it perform quite well on battery.