I think the StarForce was just some big scare; I installed only TmN but never detected any StarForce. However I've cleaned up just in case. I now realize that my friends had installed some of the other demos where I did not and that could be where the StarForce came into play. Panicking and pissed off they purged everything Track Mania related from their systems.
I enjoyed the game (especially building my own tracks), however the game was actually pretty demanding on my system, I generally had to sacrifice settings or resolution even with my 256MB X800XL (rest of my system is pretty much top of the line). It also heavily depends on the tracks you end up playing. Huge tracks with a lot of unnecessary details and decals will really slow down performance (as will large servers with a lot of players).