I know there are some minor suspension differences between the base and GT, but has anyone experienced both? Is there really a noticable difference in the drive of the two?

I think GT does have a diff suspension, prob not much of a diff. I had a 2000 pontiac and a friend of mine had a 2001 GT and the suspension was a little lower and tighter. If that helps....

Funny, I test drove the base and bought the GT out of the showroom! I didn't notice too much of a difference exept the GT seems a bit tighter in the corners.

For me the suspension difference was like night and day. That became one of the major reasons I went for the GT. The springs are firmer in the GT.

I agree. I was also told different brakes, plus bigger wheels.

The gears are different too:
3.05 in the base
3.29 in the GT

Hence the difference in MPG and acceleration.

Right on Monk! I forgot about the gears. Can you get traction control in the base? Anti-lock?

Antilock is optional on base. The traction control system that comes on the base is called Enhanced Traction System (ETS). It only does an engine torque reduction, trans upshift to limit wheel spin - it can't apply brakes like the full function traction control system on GT does.

GT has the manual mode, spoiler, chrome exhaust. And the other things that were already mentioned