I'm going to Bali in the next month and want to know what the situation is with Uber, Is it legally accepted? I've heard you tip the Uber drivers?
I believe it is legal at the moment, at least in Ubud, but there are signs posted everywhere in Ubud (as of last week) asking people not to use them (and Grab).
I didn't use them myself, but looked at the prices- they seem quite low and I would guess much more reasonable than one would get as a naive tourist bargaining with a random taxi driver on the street. Perhaps too low. There are also some stories about Uber drivers asking for more money. Grab seemed a bit more expensive for the same route.
Availability was there- but the area was not swimming with drivers, as opposed to the taxi touts who are ubiquitous, if rather low key (most hold up a laminated sign and only about 20%-30% - still too many- verbally accost pedestrians).
Note that since May 2018, Uber has ceased operations in South East Asia. You can try to use Gojek or Grab.