I have it and I have used it, well worth the money IMO.
I initially called Seat Assist (free with my service) so they came out to try and diagnose the car on the driveway. They said it was better to get the car recovered so they arranged a recovery truck then a hire car, all sorted within a couple of hours. The car was sorted really quickly at the dealers (prob because Seat were paying for a hire car by the day) with no cost to me.
If you price some of the main parts, the warranty is worth the money if something goes wrong.