I've put a few in other people's guitars and a few in mine. Here's what I noticed with the GFS pickups:
The hotter you go, the muddier they get. I know this is true in general with all pickups, but the same output SD or Dimarzio would have better clarity, detail, and openess than the GFS pickups.
Sometimes the screw holes on the plates were off a bit. Maybe quality control issue? They still fit, but seems there were wide tolerances, and maybe sit a little cocked, or needed a pickgaurd routed a bit for the pickups to fit (due to bobbins being a little wide).
They make a ton of models, but I would stay on the lower to medium output side of things for clarity and detail sake.
I have a GFS Fatbody tele neck pickup that ended my search. The bridge was knocked out by a Fralin, but the GFS neck pickup was better than the Fralin. Go figure. If your looking for a clearer, juicier, more strat like tele neck pickup - get one of these.
I think they are a good source to try different styles of pickups for your particular guitar. Ask yourself how many sets of pickups you try out in a guitar before you hit the right combo. I'd rather spend $60 on a pair from GFS than $200 on a boutique set 5 or 6 times over. Figure out what magnets and winds you like in that guitar and if the GFS pickups aren't all the way there for you, at least you narrowed down the field when you look for pricer pickups.