I guess i am obligated to chime in here given my job. First of all pat, the majorirty of policies in force (about 70%) are actually written through captive and independant agent's (captive being something like allstate where they only write for that company, independant write through multiple companies). Regardless of the fact agent's can be very hit or miss. Some are excellent and get things done correctly and on time, others are abysmally bad.
Personally i can vouch for Progressive's customer svc dept, we are here 24 hours a day and we can do anything neccesary to your policy, such as add and remove vehicles, payments, the usual. I'm sure other companies like GEICO or Esurance are probably pretty good, but there is a reason Progressive is rated #1 for customer service. Moving along. I would definitely go with a company that is 24 hour customer svc, not just claims, simply because most agents close at 5-6pm.
Keep in mind when people are telling you about their experiences with insurance companies that you should take everything said with a grain of salt. EVERY insurance company in the existence of man is going to have a person who had a terrible claims experience or customer service experience that is going to tell you they are the worst company in the world. That doesn't mean that what happened to them is the status quo.