Hey all, I'm also one of the developers. So excited that others can finally jump into our game. If you have any feedback or encounter any bugs we'd love it if you could post here about them, we'll get onto fixing any bugs asap (we tested heaps but some always slip through).
Release thread over here. No bugs thus far, some performance issues on my ageing iPad 2 (to be expected); menus sometimes lag/freeze soon after launch, some frame drops during the start countdown but everything is smooth once the races get going. Will play around some more on a 6 Plus later but not expecting to run in to any such issues on that, at least while it's running in iPhone 5/5S res.