We've owned our GB36 for over 16 years now. In our experience and observation GBs are very high maintenance boats. Not mechanically, but aesthetically. They have a rainforest of external teak trim to keep up unless you get a late 90s or later model that was ordered with mostly stainless rails, or find an older boat on which a previous owner has replaced the rails with stainless.
If you like working on wood, as I do, then it's fine.
The older the teak deck gets the more maintenance it will need because the seams will start needing replacing or repair. Not a hard job but a long one, and if you don't do it yourself, a very expensive one. And if you don't keep after the seams and plugs you'll start to get leaks though the main and flying bridge decks into the interior of the boat. Unless you get a very recent GB that was made after they started gluing the deck planks down instead of screwing them down.
On the plus side there is an excellent GB owners forum with a lot of very experienced GB owners, including ex-shipwrights and yard owners, to provide advice and guidance on virtually every aspect of these boats.
But if you aren't going to keep it in a boathouse, a GB, particularly an older one, is a never-ending maintenance job thanks to the weather, whether you do it yourself or hire the work out.
I rarely recommend a GB to people asking about what kind of boat to get, partly because of the upkeep issue and partly because of the wet-boat and rough-water ride issues. In any kind of a windy, choppy condition, about as much water comes onto the boat as goes under it.
Well, not really. But we have a five mile run every time we go out or come home across an often windy, choppy bay, and even on nice, sunny days we frequently have the wipers going all the way across and the decks are running with water the whole way.
Some people don't like the GB's ride in rough water. Like most semi-planing hulls, the GB's hull has a snap-back roll, as opposed to the gentler roll of a boat with a more rounded bottom. We don't mind it but some GB owners do.
The advice I always give people who are contemplating buying a GB is charter one before buying one. The boat has a deservedly good reputation, but it has enough drawbacks and quirks to make it worthwhile for a potential buyer to live with one for a week or two to see if the hype truly lives up to the reality in terms of what they want in a boat.
Some people find that it does, some people find that it doesn't. But better, I think, to find out before one plunks down a bunch of money for a boat they then discover is not really what they had in mind in terms of a cruising boat.
In my opinion a GB is too small on the inside for a liveaboard unless one gets a big one; 46, 48, 49, or 52 feet. Of course this is totally subjective; some people have no problem living on a 28 or 30 foot sailboat.