I have been with Metromile for 1.5 years now and only have good things to say.
Before Metromile, I was paying ~$100 per month with esurance. Now I do a ~$33 base pay plus 3.8 cents per mile. Since on a typical month I do less than 700 miles, I typically pay $70. On better months when I take the bus and bike more I easily pay $45. This is for slightly better coverage than before: California minimums.
If you take a road trip, they cap your daily mileage billing to 150 miles. ( I'm my case that's $6 for a long trip). They have a GPS option and a website with metrics. I turned off the GPS option, but I can still see exactly how long my trips are ( they still log the miles to be able to bill me ).
They also cover me if I drive out of the USA. And have generally the same perks as any other insurance.
Customer service works quite well via email and phone for coverage questions. I have never had to do a claim though. They are really a startup and only do the technical part, and contract the actual coverage to a third company. So I assume reasonable service whenever I actually need to file.
They have a tool to calculate if they make sense to you on their website. I found it to be accurate.