I never heard of one before this thread. Now there is an answer! I'm glad it's this simple. I even found a SharkBite one so I can install it myself. Thanks guys! :)

There's a trade off to the better production ratio eh? IMO, save yourself the hassle. Not only are you using more energy for a bit or warm water, but the rejection rate with warmer water is worse, so you'll burn thru DI media faster. Personal experience with my unit in winter vs summer - summer RO TDS @ about 14-16 degrees C incoming water temp = 1. Winter RO TDS with incoming water @ about 8 degrees C = 0. I can live with a slightly lower production rate thank you very much. Incoming TDS for the most part is in the 160 to 170 range in my humble abode. That's Kalamalka Lake water. On the rare occasion they switch us to Duteau Creek source, TDS drops to 50!

The temp of the water here entering the house is right around 4C, so it does improve production quite a bit by increasing the temp. I have a zero waste, so i have no reject water, so i guess pending on your situation and your water quality to start with, it does make a difference.

M, do you have a booster pump? Or do you run on line pressure? I guess depending on what your requirments are, maybe youd be farther ahead by adding a booster pump instead of blending your water for better production.
If you go the cheap route on a blended control, it is not very accurate, also depending how you distribution piping is done, you may find that there is a large pressure difference between the hot and cold. There are a few factors to consider, id boost before i blend. I have access to the equipment through work, thats why i went cadillac on my system. Just my 2cents.

My tap is at 65 psi and it's a 150 gpd membrane. I had a booster pump but it only improved production from 1:1.7 to 1:1.6 so I didn't use it. For me the biggest difference in production is incoming temperature. Cold tap water this time of year is 4-6C and in summer it is 8-12C. If I boost it up to 20C then my production almost doubles.

I'm not concerned too much about DI as it hasn't been a problem -even dealing with ammonia in the RO water from chloramines I just replace the DI when I replace the prefilters...it's pretty burned up by then.

My tap water is 180-220 and has chloramines so I run two carbon filters. My membrane is 4 years old or something and is running at 8 ppm last time I checked. I flush it lots. It's holding it's own. :)