I have also only doing the demo - the problem was, that if you did stuff out of the predefined sequence, for example by following the newer checklists, instead of STS-1, the "simulation" reacted to this only, when the demo felt that it is now time.
Also, aborts did not appear on the scope yet, I am not sure if this changes in the full version. I think the S3 performance mostly got slowed down by the rendering engine, not the subsystem simulation. The Shuttle is not much more complex as Apollo and NASSP even does great frame rates with emulation of the AGC.
Well, we'll see where we end in SSU, so far, the frame rates are still high.