Both Rider and Motorcycle Consumer News have done bits on insurance and what they both found is that for the best price on insurance "it depends." Both came up with several riders with different bikes and records. What they found is that each company was best or near the best for one or more particular rider but none were consistantly low for all riders and bikes. Just the oppisate, while each company had one scenario where they excelled, they also were the worst in another scenario. So just because your buddy called all around and got the best rate with company X, doesn't mean that you will get the best rate with them too, and do not need to call around, in fact they may be the wrost for your situation (bike, age, record, location, etc.).
For me, I was with State Farm for a while, but a couple years ago, I found a BIG discount by going to Geico. And when I started with State Farm I had called around, but several years had passed and several bikes had been bought and sold, so my situiation was significantly different. Really to get the best deal, you want to call around again every year or two. A pain, but is the only way to make sure you are always getting the best deal.