Hey a Garrison thread that isn't years old!
I own 3: a G4-12 I bought back in '05 - ordered from the factory, an '02 G20CE-HG that I bought off eBay in '06, and an '04 G40CE I bought off eBay for $129 last year. That's out of some 20-odd guitars lying about around here - lost count.
I like Garrisons, obviously.
Comment on humidity sensitivity is dead on. I've never had any problems with mine but I'm a humidity fanatic (trashed 2 early '70's Martins years ago before I got educated on humidity control). Garrisons are extremely sensitive to humidity fluctuations, as stated, because of the variance in expansion between the bracing and the wood (maintain 45-55% ALWAYS - buy a hygrometer!). I've seen a lot of examples of separated backs and tops at the bookmarks, bracing separation, and neck issues. Strictly regulated humidity = no problems - my experience anyway.
As for Garrison the guitar and the company: The brand is dead. The factory is gone. Gibson abandoned the bracing system. The founder moved on and was no longer making guitars last I knew. Sad but true.
I think Garrisons need a couple years to mellow, otherwise they sound tinny and a bit brittle. Not as much tonal range as a wooden braced guitar but they have a characteristic earthy sound that appeals to me. Both guitars I bought off eBay had to have the necks seriously relaxed - buzzed like hell - probably why the original owners were selling them. Factory setting with wet wood, no doubt. Fix took 3 minutes and a star wrench (. . . or allen wrench, I forget which at the moment).
I've seen people describe them as heavy, but I don't really think so. I have a Tak EF341SC. Now THAT'S heavy. Damned thing is a tank. Sounds like one too. Should be good in a bar fight though . . .
Garrisons are all solid woods (G series not the AG series). And these days - reeeeaaaallllly cheap. If you find one without humidity damage (splits/brace separations/neck issues), you'll find they're solid guitars at beach guitar prices (i.e., guitars you take to the beach 'cause you don't care what happens to them). I've jammed with the 6's and I gig with the 12 along side my custom Martin J40.
Many of them come with decent Fishman pickups too - 2 of mine did. They sound excellent plugged in.
However . . .
from a collector standpoint, I wouldn't buy one as an investment
Cogent entry.