My seat heaters worked well yesterday on a 300 mile trip back home. It was annoying to have to keep cycling it back to high though after it would go into low mode. I was afraid that they would be weak from reading this thread and others, but it actually was comparable to my '12 GC. I was glad it worked pretty well. Steering wheel heated up faster than in my 12.
Mofeen, If this is any help, When I first got my 14 Summit I was experienced what I thought was weak heating. After running them they have improved dramatically to the point were I have to go to low and off.
The steering wheel has always been quick and very warm