I use Geico and so far no problems. I had to have my windshield replace and they handled everything.
Not that you asked but I would not drive underinsured. I had a friend whose son was in a one car accident with four people. No one was seriously hurt but after medical bills and court judgments it cost her about $50000. Their policy was the AZ minimum, (I think its 35000), and so they owe 15000.00 now. The point is that for just a few dollars more a month they would not be in this predicament. I think it would have cost her about 15 more a month to upgrade to a $250000 policy. I personally carry a million.