I've got the fastar heater although under a different name, they're cheap and not built well at all but they certainly do the job of heating up the water and I like the fact they have a temp display too, I run mine about 45-50 degrees on the display and at the pole end I'm getting about 35 degrees which is luke warmish as I cracked a window a few years ago running it quite hot in the cold!!
Running at this temp too I find the Gardiner microbore and all season pole hose can just about take it without turning into silly string😂
I'd definately recommend one to anyone though just make sure you plumb it all in properly and have adequate ventilation like doors open or flue etc and be prepared for leaks when all up and running as everyone softens and loosens up!