I just ended my partnership with Uber (as an UberX driver). It was fun and I probably could have made a good amount of money had I put in the hours, but it wasn't for me. I live about 45 minutes north of Denver and I had to go to Denver to actually be busy enough to make Uber worth it. But because of the time and money I was spending to get to Denver, I didn't want to continue my partnership. If it was something I could just do on a whim any night of the week, I would probably continue driving. They actually are finally doing an official launch in Fort Collins, CO this weekend, which is about 20 minutes away. Had I known, I may have kept my account active a little longer to give it a shot.
If Uber is popular in your city and you have a nice car to do UberX, I say go for it! It doesn't take much to get started and if you don't like it, just turn in your phone (Uber gives you an iPhone). The freedom to work when and where you want is awesome.
FYI, I'm a full-time network engineer and Uber was something I always thought was interesting and I wanted to try out. I didn't need the extra money, but as we all know, every little bit helps when building for FIRE.