Share sheet extension reordering should have been included in iOS 8.0 two months ago, but somehow Apple managed to wait until November for this fix. Before iOS 8.1.1, you could tap & hold extensions in the share sheet to rearrange them, but their position wouldn't stick at a system-wide level – notably, closing and reopening an app would immediately reset the extension order you set.
In iOS 8.1.1, extensions in the share sheet now stick across different apps and their order persists across app relaunches and system restarts. Again, I tested this for two weeks on the beta of iOS 8.1.1, but I also ran tests on my iPad today and the fix is still in place.
It's nice that this is fixed but I can't help think that there are only about 10 people in the whole world that would even notice.