I just bought one off ebay. I got the cheaper model, kind of...
Talked with the tech support number I found. Apparently the one in JC Whitney is the EXACT same model GM used and was made by MicroHeat. The GM supplied unit only had one relay in it that was prone to shorting out, hence GM's million dollar recall on it. JCW has a lot of about 1000 NOS units they got from Microheat.
The ebayer I purchased from is selling the NEWER model that has 2 relays in it. That fixes the potential failure mode GM recalled them for.
Also, the unit has a flow control that senses when washer fluid is needed and then heats up in about 8s. The tech told me the recommended operation of the unit is a quick pulse from your wipers, then wait 8 - 10 seconds, then wash as usual. That will give the unit time to heat the fluid. It has a 70 (!) amp inline fuse, and draws 60amps on demand. No standby mode.
I should have one in a few days and will report on it's performance then.