Guys that I know who have the Grainfather love it. The only issue I have heard is the long-ish time it takes to heat to boil and the lower boil rate (more of a simmer). Wrapping the device with an insulating jacket solves the issue I am told. Wort quality is not an issue - I know one guy won medals brewing beers with the GF.
I've had it for a couple years and had very little go wrong. I will say that doing big beers on this kit is difficult without adding DME. 5-7% beers are fine 8-10% are challenging for me but I rarely brew that big.