If your into Karting then PiBoSo's worth checking out.  Here is a a comparison of the sim versus reality.  Thats putting your money where you mouth is.

PiBoSo has released the fifth beta of his Kart Racing Pro simulation, adding some new features and various fixes to the title that is scheduled to leave the beta stage soon.

Most importantly, the new version introduces the new dynamic marble build up feature that was shown off recently.

PiBoSo has released the changelog of the upcoming fourth beta version of his Kart Racing Pro simulator.

After beta 3 added a new kart chassis and lots of improvements, the fourth beta brings plenty of changes as well, including weather conditions and a dynamic track surface.

Changelog

- separate weather and track conditions, with dynamic track surface
- gearbox code revised to have neutral between 1st and 2nd gears.
- paints directory structure revised to make installation a bit easier
- support for multiple track layouts and layout editor
- server option to force a limited number of tires for each event, and possibility to re-fit a used tyre set