The catches: $100 deductible. The free roadside/towing/rental only goes up to 100,00 miles, and eventually you will reach a "break" point. Example: If a whole new engine is needed that costs $4k, and your blue book value (or maybe black book) value is below that. In that case, they give you the car's value and call it a day.
Oh, and you HAVE to get an inspection at the dealership every 5 years.
For my Patriot, (I think I paid $1200), it's probably saved me $5k or more. Replaced transmission, bearings, accelaration module, and others. It's $100 a pop.