I was on crutches for 9 months and took cabs daily to work from near mission and 23rd. All these cab companies are utter assholes: I booked cabs 3-5 days a week, from a population hub, and tipped well, but none of them could provide decent service. Each one would say "10-15 minutes" when I would ask how long the cab would take to arrive. I collected stats for a couple months: the median time was over 30 minutes and the 90th percentile was 1.5 hours. I even had a cabbie come more than 50 minutes after promised; I'd already begged a friend to drive me to work. Dude had the big old brass balls to call my cell and bitch that I hadn't cancelled, after I'd waited over three times their maximum arrival estimate. One dispatcher even admitted on the phone that they just tell everyone near where I live 10-15 minutes.
Uber in other cities may have a harder row to hoe, but in sf, merely being a cab that comes (or -- and this is amazing -- treating your customers with a tiny bit of respect and telling them you won't come if you can't) gets you really far.
Fuck sf taxes -- yellow, desoto, luxor -- I hope all those assholes get unemployed. I'm not sure Uber is a good thing in a city with working transport systems, but that doesn't describe sf. They made my life even harder than it already was; there's no good reason I should have had to call cabs more than an hour and a half before I wanted to be to work (an 18 minute drive) just to have a greater than 90% chance of making it. And when you have doctors appointments or surgeries or something else with a hard start time, I have no idea what you're supposed to do in sf besides use Uber. Hire a black car maybe?