It was discusse a bit here recently:
http://www.greenhybrid.com/discuss/h...ended+warranty

I personally didn't get the extended warranty.... because of my great past experiences with Honda, and because the battery already has a 8/80 warranty and the powertrain has a 5/60 warranty.

If you decide to go for the extended warranty however, refuse when first asked, and they will likely knock a few hundred off of the price. They have always done this to me.