I've had my "stuff" insured by State Farm since 1980. Boat's been on since we got it in 1986. We've made 3 boat claims to date (each $1,000+) and never had any problems. We have an "agreed value" policy which I review every year with my agent. I'm a big fan of this kind of policy because there is absolute certainty how much they will payout in event of a total loss. BTW- they do require documentation of any improvements if it's a restored or refurbished vessel (like mine).
I think the agent is one of the most important parts of any insurance policy. A good one will go to bat for their customer, even when it's against company policy (it happened to me!).