GT? I've had a few...... and still got them.
In my opinion they make great, no-nonsense bikes. I got my first, a Zaskar LE MTB, back in 1994 and it is still kicking ass 20yrs later. I bought a Traffic 1.0 hybrid at the end of 2010 and after a few initial teething troubles that has also proven to be a very solid, reliable and enjoyable bike to ride, now approaching the 10,000 mile mark and no plans to replace it for a long time yet! My roadbike was bought mid-2011 and is the GT GTR3 that has covered around 1500 trouble free miles and is a joy to ride fast. The hybrid and roadbike were both bought towards the end of the model season with reductions of around a third off RRP which I think made them good value as I thought the RRP was a bit too high but not out of step with similar offerings from the other popular mainstream manufacturers. Having said that, at the time, the GT range was probably slightly better specc'ed than the competition but I have noticed a distinct drop in the component spec in the last year or 2 to keep within the targeted price points (lots of Formula hubs and Microshift brifters where there were previously Shimano items fitted).
I also bought a junior MTB for my kids, A Stomper 20. This 20" wheeled, 7spd mini MTB has been hammered by both my kids as they learned to off-road and has now been loaned to a friend and is still in great shape. It's a real tough bike and both my boys were reluctant to give it up when moving to bigger bikes.
In terms of quality, history and market support then GT are equal to the likes of Specialized or Kona and are certainly worth considering. For some reason they just don't seem to have the presence or impact of some of the similar brands despite making great bikes. Maybe it's because the bikes are just good without gimmick or razzamatazz that they get so overlooked? Despite this, they certainly are not dull to ride!