To follow up on my last post, this modification is worth doing in my experience (1.5 months). Again, compared to the LR gray soft spring thermostat, this inline kit runs pretty similar temps, but just a tad lower. Nothing drastic. What I did notice is, once you hit sub 90 degrees ambient, the inline will run about 5 degrees cooler than the gray stat (183.1 vs. 188.5). Honestly though, that's not when it matters so that's a wash.
The inline kit does react faster. After idling in traffic in 108+ ambient, I'll see 199-205 and it will fall back down to 197 in a few seconds once I get moving.
Where I see little difference is huge mountain climbs (25% grade for miles and miles. Mt. Ord if you're from AZ, you know) in the heat (105+). The inline is about the same as the gray. I'll see 210 and as high as 215 with both. That's when I hit the magic econ button and kill the AC compressor, bringing temps back down to sub-210's and my family complains about how hot it is. But then I point out all the fools on the side of road at the top of the hill with their hoods open because they overheated. Suck it up kids! It's not just Land Rovers.
Anyway, this inline stat is good, if only slightly better then the gray one. If anything, I do like it's simplicity. It's staying on my Disco.