I have my two week old Giant and I'm very happy with it. My fitness levels have started to improve noticeably. I'm working my way through the gears and even get to 21st going downhill. From being able to ride for only a few minutes, I can now ride for about 25 minutes.
I'm actually now finding that I don't use the small front cog at all. My concern now is that as I get fitter, I may want a higher gear set. Is my bike already decked out with the best gears or can I whack on a different cassette?? is it? or am I peeing into the wind and looking at another bike altogether?