On one hand, it destroyed the livelihoods of many people. On the other, it made ordering a taxi so easy that a lot of people stopped driving home from parties drunk.
Uber has also made getting around in a lot of cities much safer. I've gotten into taxi's with drunk drivers before (seriously wtf), not a problem with Uber, or at least not for very long. (When I reported the drunk taxi driver, turns out the medallion owner wasn't working that night and had lent his cab to someone else, there was not trace of my ride or of the driver...)