"Worth it" is a relative term. For example, I don't think it's worth $250 to swim with dolphins, but for others it's the experience of a lifetime.
That being said HECK YEAH it's worth it!!!!
I did the 8 lap rookie experience last September, paid full price, and never regretted it.
There's no danger of that 3 hour experience getting you a Nextel Cup contract, but if driving and racing is your passion you really need to give it a shot.
Driving out there behind your instructor at 125 mph (124.89 in my case) gives you a lot more respect for the pros swapping paint at 190.