4 years for $400 isn't bad. If you can trust your dealer and mechanics and don't like working on the bike yourself, go for it. I'd recommend looking at the service department at that and other local dealers. See how the bikes are treated when mechanics go for 'test rides' and try to talk to other customers. You'll want to be able to use that warrantee if and when the time comes and don't want to be served with the runaround or bad service leading to more problems coming out than going in.
I say go for the warranty. if you sell the bike it adds to the retail value. I bought one with mine.