Jon probably has more track time than me with the rack, but I just got back from Watkins Glen and thought I'd post up my impressions.
This really is a great mod for a roadcourse car. The Glen has some pretty tight turns, but I was never wanting power steering. The wheel has weight, but steering inputs were easy and the wheel felt very controlled and smooth, even with my wide tires. I'll be interested to see how it feels on NHIS, which is a smaller and more technical track, but right now I don't have a single complaint about the rack in a track setting.
The only thing I want to mention is it's behavior during spins. On my very first lap I misjudged a corner and oversteered considerably. The wheel got ripped out of my hands and I was, for a moment, trying to control the car with just the throttle while I got things under control. With no power assist, the wheel will get the best of you if you're not expecting it.
After that, however, I drifted and slid through that same corner a few more times with no problem as I was experimenting with line and turn-in. I think a spin that requires a lot of countersteering to correct would be a touch difficult with the manual rack, but, then again, one shouldn't be at that slip angle anyway.
Clint