All in all, it's a great car except for the rear brake problem.
I own 2-2009 Sonata GLS. The first had a rear caliper problem early on. The second, has had the same problem as of late. I've been to lazy to replace until now.
My right rear caliper would freeze and would wear the pad prematurely. It would wear into the rotor in under 2k miles from new.
A few days ago, I replaced everything.
both rear calipers,
both rear brake hoses,
2 cans of brake cleaner.
I got everything at Advance auto which is local to me. Found some online coupons.
My total out of pocket was just shy of $200 for everything. I did the labor myself. Took about 2 hours in all.
If your having problem with your brakes, just fix them yourself. It's easy enough. If your a novice, check youtube. They have lots of videos and some are specific to the Sonata.