Ok so the short answer is, it's up to you, and depends on how you feel about extended warranties. Although this is not an extended warranty, this is an additional cost outside of the vehicle price.
My beyond .02 is...
We bought the prepaid maintenance for my wife's Ford Edge. That plan is AWESOME. It covers, tire rotations, oil changes, air filters, cabin air filters, wiper blades, brake pads (not rotors), and even shocks. I priced all the services independently and this seemed to be reasonable.
So, I went looking for something similar for the Sonata. As far as I could tell there isnt anything that extensive. What I bought was Vehicle Care from Hyundai. You pick the mileage to limit, and interval, and tires and oil, or just oil change and that's it...
I dont have the specifics but I realize I overpaid on the services. However my dealer also gives you a service coupon booklet for $25 off each severe mileage interval service. I negotiated that since I was already paying for tires and oil change service that I should be able to keep this too. So each visit I give them 1 coupon from vehicle care, and 1 coupon from their service dept. They have said I could accumulate the service coupons to use for anything they do like purchasing tires, or fluid flushes. So in the end, they're subsidizing my maintenance up to 60k miles.
Not bad in my opinion.
Good luck.