Im insured with State Farm, and when i purchased back in Jan, 2006, my rate only went up $100 for the year, and I was driving a Jeep Liberty before that.. I have full coverage, rental car, and have my homeowners insurance through State Farm.
In my experience, State Farm is the best insurance company out there for autos based on cost of insurance, and the protection they provide. My wife works for Nationwide Insurance, and says how easy it is to deal with State Farm, and State Farm pretty much gets what they want when defending one of their insured. The $10, $50, or even $200 you may save by using one of the non-standard insurance companies is not worth it if you have to file a claim someday.
My experience:
I was parked in my RL and a semi driver hit the back end with the edge of his trailer. It damaged the tailight housing, and scratched the bumper.. no big deal, it was about $600 to fix. It was the truck drivers fault, but still when it came time for the jag truckdrivers insurance company to pay up, they wanted to settle, and pay less, and not pay my deductible. State Farm told them no way, and sent it to subregation(sp), meaning they were ready to go to court to get back my entire deductible, and make this truck drivers insurance pay for all the damages. State Farm, and I won, got my deductible back, and my RL fixed %100.