I have a gt series 3 that I bought when I first started riding. I've since upgraded it to sram force, and when ridden with good wheels it's totally passable. I did a double century on it when my primary bike was out of commission, I've done RR -type group rides on it, etc.

Only time I ever felt anything amiss was on the double, a crazy descent where I hit a corner too fast and had to brake hard, the frame felt a little noodly. But, I was also on a borrowed front wheel, which could have been the cause.

oh, and because there's never going to be a "show your GT" thread: