I did a day at Thunderhill in September and experienced the sticky clutch pedal and missed a shift down the straight. I just did another at Sonoma Raceway this last weekend. Between this and last track day, I did two things people have been suggesting.

1) Removed the clutch assist spring
2) installed the Whiteline transmission mount insert.

While it was cooler this time around at Sonoma and has less straight line areas, the experience was MUCH improved. I didn't feel like the transmissions was fighting me during shifts. The gears always were right where I expected them to be and no problems with the pedal either.

I don't have an upgraded clutch line or anything else fancy except a short throw. I'm pleased with the result from these two very inexpensive and very easy modifications.