I think it really depends. I know I have been looking for a new set. The stock seats in a 2g are horrible compared to those in the 3g. They are very small and uncomfortable. Being 6'5...I really need to get seats that sit me lower to the floor and offer better support. While I am nowhere near ready to take this car to the track, the seats are very practical and would make the car that much more enjoyable.
With the height problem, I also have to think about the steering wheel. When I go with a smaller wheel, I will also be losing the airbag, meaning I will most surely be going with a 3 or 4 point harness. Anyone who has ever been up close to a 2g knows the back seats are completely worthless anyways, so I'll be able to get away with a harness bar.
I don't think any car modification can really be considered a waste of money....especially if it increases the happiness and excitement of the person behind the wheel.