I agree with most of the comments really - they're decent meat & potatoes, workmanlike guitars. Built to do the job, but not much attention to fine detail. Tools, not works of art. They're very much handmade - so no two scratchplates are ever quite the same, and the pickups look like some sort of science project (although they sound good).
Having said all that, I've only owned bog-standard models like the GS-1 and GS-2, not any of the more upmarket models.
The thing I could never quite understand was that they were always described as great value for money. Maybe compared with the RRP of big-name makes, but you hardly ever see GS guitars heavily discounted like Gibsons, Fenders or other brands.
I don't think they're as good value as Japanese guitars. OK, one's handmade and one's mass-produced. One's buying British, supporting small local businesses etc., and the other... isn't. But for what you end up holding in your hands, I think GSs are actually quite pricey.