I am replying to this old thread,as the app has now been updated and we finally have this functionality, to use the RAM preview like a regular editor. I love how AE can now playback footage in realtime (on my 3xioFX RAID set up anyway).
To get it working:
In the Preview panel:
-Select Spacebar from shortcut
-uncheck cache before playback
-Range = entire duration
-Uncheck If caching play cached frames
-CHECK Move time to Preview time
very useful for adding GFX at the right time quickly.
Now if we can get audio scrubbing to work smoothly while holding ctrl we will be there!
Tris