I know if you toggle video effects on or off during playback in version one, that playback will stop, and I'm pretty sure it will stop in other versions as well, until you get to version 11. After stabilizing some video with Mercalli, I played back the timline and decided to turn off stabilization by clicking the "eye" icon. Surprised was I when playback didn't stop. On, off, on, off. Playback keeps going.
I'm also surprised that PRE11 is much faster stabilizing my DV-AVI video than Sony Vegas Pro 12. I don't know what is going on.