According to the reviews at Newegg, Gigabyte's thermal paste on the 685 (WindForce) isn't too efficient, and can be replaced with a better TIM (have a tube of MX-3 myself).
I suppose cooling design on GPUs is nowadays similar to the CPU world when it comes to general heatsink solutions and mounting to the actual heat source. How easy is DIY installation though? Can you just rip off the HSF, change TIM and reinstall without too much hassle, ie. just as easily* as you'd do with an aftermarket HSF for a CPU?
What kind of thermal paste do other vendors use on their cards?
* = done that twice over the years, usually the biggest hassle in building h/w, and never goes just right the first time around
Yeah its actually preety easy. Just unscrew the cover if it has one, unscrew the heatsink and you will see the thermal paste. Clean with alcohol and apply yours. I tried it on my 5770 with arctic silver 5 and it doesn't do that much. If you have high temperatures than its worth a try. I'm preety sure the thermal paste vendors use is trash.