What browser are you using? I'm using a chromium based browser and I don't see any noticeable input latency.
Hmm, I'm not sure then. I noticed that the steering and acceleration can appear delayed since they are implemented via a physics controller, rather than a kinematic controller.
I'll be uploading a new build fairly soon. If you'd still like to try it out, perhaps one of the downloadable versions will work better for you.