Join Date: Feb 2008
Location: Ellicott City, MD, USA
After getting a quick flat and almost wrecking my other bike in a corner, TPM was a must-have on my GT. TPM would give an early warning of the pressure loss.
I also like the ASC. I use my bike to commute often, and have had it kick on in the rain several times on slick surfaces (leaves, tar, etc). I don't know for sure that I would have wrecked without it, but it definitely does its job (well).
Both worth the money IMO.