Hi Keith,
In your export settings, you can choose to use preview files. In CS5 it’s a check box, in previous version it was part of a contextual menu on the right side. While this will vastly speed up your render if your timeline is already rendered to preview, it will essentially compress twice and that will affect quality.
H.264 looks good, but it take time to render to it. More effects like Magic Bullet can drastically slow things down. More processors and some newer GPUs can accelerate that process.
Vince Becquiot
Kaptis Studios
San Francisco – Bay Area