I know nothing of full suspension bikes Dan, I dont know much about MTBs full stop (well the hydraulic brakes and forks are a mystery, I understand hydraulic basics but that's about it, and I haven't got round to working out rebound settings and such like. I like the way mine's set up so leave well alone
).
I have a Giant XTC3.5 as well (2008 model bought cheap last winter as they wanted to get the new models in) and it does everything I want it to.
I've recently cut the bars down by an inch and fitted a short stem to get it more to how I want as it's a small frame (oh surprise
) but the bars felt way too wide and I didn't think the stem was suitable for the frame size either, went shorter for nice quick duck and dive handling and on the couple of run outs it's had since the changes is much better.
Personally I like a hardtail, it feels nice and involved and I don't ride any ridiculous downhills as I don't want to risk injury. I happily chuck the bike about Surrey Hills and local trails at reasonable speed and with a fair amount of gay abandon, full suss might take some of the fun out of that by softening it up and making it too easy. It's only stuff like Deliverance at Leith Hill that I leave alone. If/when I get an upgrade it would be to a better frame but I'd stay hardtail and go for something like a Cotic Soul or similar and some better brakes as the XTC has standard Giant ones which are now an "older" model and the pads aren't as easy to get hold of.
Sylv, Grahame, Marco, Dombo or another proper MTBer will be able to fill you in of something big and bouncy
.