Toxik can import QuickTime files but as of the current version you cannot render to QuickTime only sequence files.
As far as the framebuffer, first let me remind you that the MAC version is still in beta with that said Autodesk knows and understands that this is a highly requested feature. There are plans to have frame buffer support through QuickTime, essentially a wrapper around a Quicktime Video Output component.
Ken LaRue
Autodesk Application Engineer
Toxik / Combustion
Training DVDs =
http://www.thestreetproductions.com 
