I have a 2010 Lexus ES350 and my 6 month premium (paid in full) was $866, which is about $100 higher than I was quoted on Esurance. However, I signed up for the Snapshot program to potentially saved 30% off the $866. I read a lot of negative reviews about Snapshot but when the Progressive agent explained the three factors considered, I decided to try it anyway.
First, they measure the time spent during high-risk hours (midnight to 4 a.m.) -- I don't ever drive during those hours, so I have zero minutes.
The second factor is the amount of miles you drive per week (they want you to be under 50 miles per day, and preferably under 30 miles per day) -- I drive 25 miles a day on average during the week and even less on weekends, so my weekly average is about 150 miles.
The third and toughest factor is what they consider hard-braking, which is slowing down at a rate of speed greater than 7 mph per second. In other words, if you slow down very quickly, it will beep at you and you have accumulated a hard-brake. I do not rush up to stoplights and brake fast and I don't tail people and I roll up slowly to stops, so my average is 1 hard-brake per week (sometimes it just can't be avoided).
After 30 days, Progressive gave me my estimated 30% discount and I was immediately refunded $251 of the $866 that I had paid for my 6-month premium. They require that you keep the device on your car for 6 months before your discount is permanent.
I think that if you're a good driver, a safe driver, and aren't driving a lot or out past midnight, then this is an excellent way of cutting down your insurance cost. Thanks, Progressive!