I have used Uber in a few different places and actually quite like it. The only hitch is obviously you need wifi or 3G so when traveling in new places you may not have either.
But it is a lot cheaper and widely available. I used tons of uber in Johannesburg and I felt safe. In fact, the drivers were very professional and made sure to wait for me to enter the destination so I was safe.
There have been some recent backlash here in Canada due to a report of assault but im sure these things happen in taxis as well so its a risk that comes with the territory.