The car will be due an inspection/service every 12 months, depending on mileage covered will depend what needs to be done.
Generally the car uses oil/brake fluid with a 2 year life, or 21k miles for a diesel, so generally it works out as as basic inspection service one year (or in other words, very cheap) then the following year a full service and brake fluid change, filters etc (or in other words, very expensive). My first year "service" was about £50, the 2nd about £350 as it needed oil, brake fluid, filters etc. I gave it back before the cheap one came around again (if the new owner reads this, you're welcome
As to whether the warranty is worthwhile, really the only person who can decide that is you. See what it covers, see how much it costs but most importantly, check what it DOESN'T cover so you don't have a nasty surprise if something breaks.
I've personally never seen the point but YMMV and all that.