I have an '03 20th Anniversary VW GTI.
I have taken it to 121 mph and have cruised at 100 on the turnpike for about 10 to 15 mins at a time. It is just too enjoyable to me.
I drive 70 - 80 in most places anyways and gas mileage isn't that big of a deal (25 to 28 mpg)
It's just that with the 6 speed and turbo I want to use it as much as possible and enjoy driving it at high speeds. Unlike some cars, at 100 mph it feels quite civil and there is not too much noise or ride harshness and it feels comfortable (and of course quick).
Also, I would probably get on the highway by getting up to the limiter (131) and then cruise back down.
I am careful (and weary) of traffic however, and would probably just cruise at 80-90 in most cases.
There's nothing like hitting the onramp, being sent backwards into your seat, and watching the tach hit the redline, shift, feel the tires scramble for traction, and realize I still have 3 gears left!!
One of my friends drove it, he just went into fourth, and I said you're at 95! He looked at me in disbelief and smiled. He then looked at the speedometer and his eyes openned and he said "oh crap, your're right".
Not a big fan of street racing though, keep the streets safe....