Idk, if your car is modified, is in a very hot climate, tows heavy loads, etc, it can be of benefit. I have a lower-temp thermostat (170*f) than stock on my 328, along with a Fluidyne radiator, aluminum expansion tank, Samco Sport silicone radiator hoses and all coolant lines, brass bleeder screw, Stewart WP (and lightweight 20% underdrive pulleys), amongst other things, and my cooling efficiency improved notably with the same ratio of BMW coolant to water (40:60 coolant/water). Numbers being a solid 15*f drop at 95f ambient on the track.
Adding Redline Water Wetter has resulted in a further 6-8*f drop under same conditions, as monitored by a digital/analog-combo gauge. The combination has also dropped oil temps by 10-12*f under heavy load. I am looking forward to trying it with a 98/2 water/coolant mix, or even pure water.
I use it in all my cars, and have for over three years. All cars have had at least one flush since, and there was nothing at all like the black gunk people have said it causes, even in my Camry and Contour which are the only ones with a 50/50 mix (Bimmers get 40/60).
It is cheap, I have had good results, and the extra few seconds it could give between a cooling component failure and overheating might be exactly what is needed to notice and turn the car off, preventing a blown HG or worse (bent rods, etc). Cheap insurance.