Just used my Brew Jacket for it's first, full batch, a California Common. The fermentation room ambient temp is about 78F right now, and the Brew Jacket is holding 60F without working hard. In fact, it hold the set temp within a degree--verified with my reference thermometer.
Used it on the secondary of a Belgian Wit to do some cold conditioning, mostly because I could not wait to see it in use. It held 50F for two weeks, no problem, and the beer noticeably benefited. I have no doubt I could do a 'full' lager in the Las Vegas summer if needed. I may do an Oktoberfest type beer soon for the Fall.
I used to use a Cool Brewing insulated container to ferment in using ice to cool & control fermentation temps. In addition to not having to change the ice every day, the temp stability far surpasses the ice method.
So, no, the Brew Jacket is not hype at all. I may even get a second one when they offer them for sale normally. So far, I am thrilled with it. I have easy and highly controllable fermentation temp control for the first time.