Version 0.5 finally has sound, and the extra car and track plug-ins finally work. The game is slow, however; it runs at 10 fps on my 800 Mhz 512 MB RAM iMac, some cars don't work (due to version differences), and it's difficult to configure preferences. Still, it's free, and due to the huge amount of extras you can get, it's worth a try. The mouse controls are a little tricky at first, BTW.