I use Uber, Sidecar, Flywheel, or Lyft at least 3x a week. I used UberX yesterday to transport some new large luggage that I bought. I believe all of these were invented in SF, naturally; I know a couple of folks that work at Uber. Lyft is like UberX, but drivers are mandated to attach a pink mustache to the front or windshield of their car so that they are visible as Lyft drivers. Sidecar is totally discreet and Flywheel has the support of taxi drivers (usually impossible to call a taxi on Uber, SF is the only city I've been able to so far and it's a difficult).
I used Uber in Atlanta when I lived there, but the only options were for Uber black cars at the time, though I recently used UberX there in September now that it's available and these drivers were such novices. Had no idea how to get around the city, not to mention there were basically 2-3 drivers in total on a Saturday night such that my crew and I ended up with the same black girl and her Dodge Charger like 3 times. Needless to say it was an interesting night and we loved her for it - she charged a lot less in Atl than in SF, despite the distances to go anywhere and she was a chatty cathy in a good way.
But Uber presents 4 options in typically large cities:
Taxi - where you can call a taxi to your location (often not available in cities where there are disputes about all of this)
UberX - random drivers in their personal cars; they must apply and pass background
Black Car - town cars, this is very popular option in bigger cities where 10-15% of the cars on the road are town cars (SF, NYC, DC); I used once to impress a date in Atlanta before anyone there had even heard of Uber - knew my driver's name and number and pretended to know him personally until I decided the joke was over, LoL
SUV - limo SUV's. Was the only option available for me and my crew once after a concert, so I bit the bullet and ate the $223 fare to transport us back a few miles to our friend's apartment.
There's your rundown. Keep in mind that while you rate your drivers after all is said and done (1-5 stars), they rate you as a passenger. Fuck up too much and you're rating will dip too low for anyone to want to pick you up. If you are drunk with friends or a hookup at 3 in the morning on Fri/Sat, I suggest you still take a cab! Cab drivers are much more forgiving and look the other way if you want to break out the blow or get a blowjob in the backseat. JK JK JK