The dealership in Central Florida I bought my Spark from was pushing the extended warranty really hard. I didn't want it since 2 years seems plenty to me and I like fixing my own stuff.
There's really no reason to buy the extended warranty until you are near the end of the factory warranty anyhow. The way I understand it, the extended warranty does nothing until the factory warranty runs out.
I'm not sure what company actually administers the extended warranty though.