Shifty
At the moment, drivers can pick their shifts, and if not busy, won't make minimum wage.
That was was of the arguments during the UK London court case, the drivers weren't working at the busiest times, therefore technically being paid less than minimum wage, but that was down to driver choice. They lost that argument, but I'm still not 100% why.
If Uber are classed as employer, then I'm guessing it will be down to Uber to dictate when you work. So that will be every Friday or Saturday unless you want to use your holiday pay.
They won't pay you for sitting around during non busy times.
These arguments aren't going away any time soon. Where I live Uber has forced the other taxi companies to offer competitive rates. So ringing the local taxi company no longer costs you triple. So I guess there is that.