I finally got the thermal pads in the mail last week and installed them in a GTX 1080 SC just to see if temperatures would change.

The installation process was pretty straightforward; the only bothersome step was reconnecting the fan and LED leads back into the PCB. I opted to use Noctua's NT-H1 thermal compound that came with the NH-D15 cooler instead of the compound supplied with the thermal pad kit. The kit included the pads for the backplate, VRMs and the RAM chips. After taking the card apart, only two of the stock thermal pads made contact with the RAM chips. (no imprints on the factory-installed pads).
 
The system has the following components:

• Intel i5-6600K Skylake CPU (currently at stock speeds, but it will do 4.7Ghz stable at 1.35 volts. 4.6Ghz stable is achieved with 1.264 volts)
• Asus Z170-A motherboard
• EVGA GeForce GTX 1080 SC Gaming 8GB ACX 3.0 GPU (card takes a max +125 offset to core clock and a max +500 offset to memory clock without artifacting)
• Corsair Vengeance LPX low-profile RAM (2,666Mhz speed); 2x8GB
• Noctua NH-D15 CPU cooler
• Samsung 840 EVO 250GB SSD (OS Drive)
• 2x Hitachi DeskStar 2TB 7,200 RPM hard drives (one for games, the other as the internal backup; also use two other external drives for backups)
• On-board audio
• EVGA Supernova 650P2 power supply
• Fractal Design Define R5 mid-tower ATX case (with two Noctua NF-A14 PWM fans as intakes, one NF-A14 FLX as a bottom intake, another NF-A14 PWM as rear exhaust and one NF-A14 PWM as top exhaust). Top exhaust and bottom intake only kick in during gaming (using custom fan curve in motherboard BIOS) and I keep them at 800 RPM max to keep them very quiet while still promoting air circulation inside the case. Front intakes and rear exhaust don't go above 900RPM.
• Windows 10 Anniversary Update

(In case anyone wants to know, the i5 idles at around 28 degrees Celsius and doesn't go above 38 degrees Celsius while gaming using stock speeds. 4.6Ghz will push the temps to 51 degrees; 4.7Ghz at 1.35 volts will take the CPU to 72 degrees max on the hottest core using AIDA 64 or ASUS' RealBench. Under typical gaming load it stays between 57 and 60 degrees, depending on the game).
 
Using the card stock (but with the new BIOS installed), temperatures fluctuated between 73 and 78 degrees Celsius under gaming load using GTA V, Titanfall 2 and Rise of the Tomb Raider. Those temperatures where at stock clock speeds and voltage; the card was not overclocked other than the OC provided from the factory (being an SC card). These temperatures where achieved using a custom fan curve with a max 70 percent RPM limit. Boost clocks fluctuated from 1,866 to 1,911Mhz.
 
Now, I live on a Caribbean island (Puerto Rico), and ambient temperatures here are hot: around 93 to 99 degrees Fahrenheit during the day and 88 to 91 degrees Fahrenheit at nighttime on 10 out of 12 months on the year. It's "winter" right now, so ambient temps range from 85 to 88 degrees during the day; 78 to 85 degrees at night. Add in the insanely high, year-round humidity and you can see why keeping computer hardware cool is a nightmare.

To put it mildly, the combination of the Noctua thermal compound and the pads made a HUGE difference in GPU temperatures. At stock speed and voltage the card now achieves between 65 and 67 degrees Celsius using the same 70 percent max RPM fan curve; the boost now goes from 1,936 to 1,949Mhz. Upping the power and temperature limit to max (120 percent power and 92 degrees temp) and dialing in a +125 to the core clock and +500 to the memory clock, temperatures stay between 71 and 73 degrees Celsius using the same fan curve with the games listed above! Overclocked boost speeds go up to 2,086Mhz (it hits 2,100Mhz from time to time) while card temps are between 40 and 50 degrees, but stay at 2,050Mhz while gaming at 71-73 degrees.

The temperature difference was substantial, so playing around with the fan curve I was able to dial in a max 65 percent RPM curve to keep the temperature at or just below 75 degrees Celsius. 65 percent RPM is not too loud (I can still hear the GPU fans inside the Define R5, but it's definitely quieter than 70 percent RPM) and I can live with that max temperature, considering the high ambient temperature.
 
Unfortunately, the card is now going back to EVGA for RMA (shout out to Joseph and the support crew) because the fans keep spiking the RPMs above the 70 percent limit established with the fan curve. They constantly go above 70 percent max RPM while the card is under load, and the sound they make when they spike (the spikes come about every 10 to 15 seconds) is ultra annoying. The fans spike even using a constant 70 percent fan speed using the slider in PXOC. I'm not happy about having to receive a refurbished card even though I bought the GPU back in October, but if I can get a card back that respects the fan curve and hits the OC speeds I got from the old card, it should be fine.
 
Anyway, just wanted to share my experience with installing the thermal pads. My guess is the thermal compound made the biggest difference, but if you are on the fence about it, I'd go ahead and install the pads and change the thermal compound for something better. The temps now are what I expected from a GPU with a custom cooler.