Nationwide Insurance is my current car insurance provider mainly because they were the cheapest. None of us like to think that we'll be in an accident, but I was in one and I'm very pleased with how things were handled afterwards.
Nationwide has local agents, which can be a rarity depending on what provider you go with, however it's not required to meet with them to set up a policy or even deal with claims. They work on whatever level you want them to.
The thing I really like about Nationwide is their Blue Ribbon program. Basically if you get in an accident and your car needs to be repaired, they have teamed with various body shops and automotice repair places and you never have to worry about filling out any forms. The shops themselves document the damage and repair it, and no bill ever comes. In fact, you pay the deductible directly to the shop. Also, a nice plus, my plan (and I think most plans) stipulated that if my car was in the shop I'd get a rental and indeed I did. This was also handled directly by the Blue Ribbon shop & Nationwide -- I never received any bill.
Nationwide also has online bill access and payment, unlike a lot of smaller car insurance firms.
Overall I really like Nationwide, not just for their low prices, but the ease with which my claim was handle. Even though my rates increased a little after the accident, they were still quite low and I have stayed with them.