Love Hertz US, but keep hearing these stories about CR.
We did Avis after talking with lots of folks and had no issues.

For the scoop on insurance (regardless of who you use), The Avis CR site has some good info on insurance.

http://www.avis.co.cr/avis_insurance.htm

As an FYI, there is an Avis Deal (look on their US site deal for international deals) that is a rate that includes all the insurance (including local), would be nice if Hertz would match that.