We are using this company. I believe the policies sold through Co-operators are with Coseco. Pretty good. We haven't made any claims so far, but consulted them recently because someone backed onto our car in the parking lot. They walked us through the options very patiently.
In terms of price, they are pretty competitive.
Funny you mentioned that the name is similar to Costco, as this is The insurance company for Costco employees. Hehe.