Firstly, I love the demo. Runs smooth at around 400 FPS with everything maxed. Menu layout is extremely minimalistic and a complete pleasure to use. Click, click and im in a scenario or the sandbox, very efficient!
User interface in-game is also very very easy to use, all buttons work and are easily identifiable as to what they do, sliders are easy to use and pinpoint accurate and labeling is clear and readable. My only downside is the tabs on the far right, the glow effect on the text makes the font a little unclear, much prefer the style used in the tutorial videos done by Killrob!
Graphics look superb, again crisp and clear, textures look very good! Cant spot any modelling errors either. Animations when testing engines are smooth and certainly pack some detail!
Sounds are brilliant, can easily tell by ear which engine is running a 2 litre race setup and which is a 1.3 econobox! Backfires really add to the effect of creating a firebreating monster engine.
My only major negative so far (Sorry, has to be one!) is the windows. I like to run my games at fullscreen, which of course you've included an option for. The game however, as I guess you've designed, then runs the scenarios or the sandbox in a window inside the game. This makes it all a little small for me on a 1920x1080 monitor and I also find still seeing the menu in the background a large disturbance and often leaves me forcing myself to focus on the window the designer is in. I feel a little mislead since the tutorial videos seem to run the scenarios in a fullscreen environment? I dont know if this is a planned feature just not included in this demo but if not, personally I'd like to see it changed as I feel it spoils the enjoyment of the game.
Overall, an absolutely cracking demo release and I hope any future updates and additions continue to make this very niche game an absolutely amazing one!
EDIT: Noticed a few views now, please give your opinions too guys! Surely it will help development, or just praise the gods who gave us this demo!