I'm definitely no expert on all the Gentle Giant lines, but they almost seem to suffer from the same thing Hasbro does in just producing too much stuff at one time. Sure, they have the sales numbers, so maybe that tells them something differently, but I'm just getting the feeling that some collectors are getting burnt out on all the stuff out there and instead of limiting a focus - in many cases they're just saying "forget it" and waiting/quitting/picking it up much cheaper via ebay later on.
In the past year or so, I've just been starting to pick up my first GG product (mini busts and animated maquettes), and I have to say I really like both lines. Going forward, I won't be able to afford to do both, but I'm hoping I can still grab a mini bust here and there. Again, since I'm just getting into this, I'm not as familiar as most - but from what I understand the mini bust line started at a nice pace, and then they started making more and more (and ridiculously exclusive/obscure busts) until it got difficult to keep up. Then they have lines out there like the Classics busts, Kustomz, Bust Ups, etc. that don't seem to have found the right audience.
I'm not sure if they are suffering or not, but I'm a good example of the secondary market prices. I've picked up five mini busts and four animated maquettes over the past year or so, and haven't paid more than $30 for a mini bust or $40 for a maquette. Basically half price or less for each of them, and not a one has been from ebay, they've been from online retailers. That can't be the greatest thing in the world for the retailers (although nice for us). Anyways, I hope GG isn't in their death throes, because I really like the OT busts, and if I could afford them, I'd grab a few statues as well. I really want to get the Han w/Taun Taun statue off their site at that discount, but the timing isn't the best for that type of purchase right now.