I've had a GS8 for a couple of years now and you're right, it does pack a nice low end wallup. From my understanding, when the GS series was initially introduced they were very hot sellers and since have tapered off a bit.
One reason a person might not choose the GS is because they're a little less amenable to finger picking. I've used it quite a bit for finger picking, but the I've heard (and this may or may not be true) that the top is cut slightly thicker and is harder to generate sound from finger picking alone. Also, the recommended medium strings can be a little difficult to pluck, especially for those of us using our natural finger nails. Having said that, some gigs I've finger picked have sounded AMAZING and blow all of these arguments out of the water. I've actually thought to myself, what's everybody talking about, this guitar finger picks like it's nobody's business. But other times I have felt I wasn't getting the best tone. So many variables effecting all of this, so who knows really?
As far as strumming goes, it's amazing for that, or for flat-picking. The bass-i-ness lends itself to some country or bluegrass applications, while it still retains the clarity of a Taylor. I've played with some old-time Martin and Gibson country players who really liked the tone, and said so...which means a lot because these guys were serious professionals back in the day...what they don't know is that I had to eq out some of my bass just to play with them...the bass can be that boomy sometimes...
IMHO, the GS8 is a great guitar...I couldn't recommend it more. But suffering with a bit of GAS, I'm still thinking about getting a 614ce or GA6 for when playing in band situations (less bass and more cut through) and for a little easier finger picking than the GS8.