also looked at the Trek 7.6 FX, which has nicer components, but the $$$ = ouch.
I was looking at buying a 7.6, but none of the bike shops in my area had one in my size, and Trek was out of them. So I got a 7.5. Which I am glad I got anyhow, I like the color better, won't show dirt as much as the Candy Apple Red color of the 7.6

And I don't need the 27 speeds anyway.
Word is (from my local LBS), that Trek is planning to have 2008 models available midsummer this year, so if you have a bike you're already using, you could hold off, and get the latest and greatest in a couple months. I didn't have a bike until I got the Trek (my x-mart special was stolen), so wasn't willing to wait.
Only thing I don't like about the Trek is the saddle. But I think most commuters end up replacing the stock saddle on just about any bike, from what I have been reading.
Oh the wheels. With your weight that *might* be a concern if you get a rack and load it up with a lot of weight. I think the Trek's wheels have less spokage then other bikes? So possible you might break spokes? Not sure about that. I asked the shop about that, they said I shouldn't have any problem loading up a rear rack if I want, I weigh a little over 180 at about 6' height. Actually thats about my ideal weight, but too much of it is in my waist, having trouble buttoning 34" waist pants now. I weighed more when I had a physically demanding job years ago, but it was muscle, so fit into 32" jeans no prob. But now I am going off on a tangent...
Well this post didn't help much, I didn't test ride a GT so can't help much with comparison. I'm not a component guru either, so can't give any definitive answers about components by looking at specs. But if you go with the Trek, I doubt you'll be dissatisfied with it.