My usual workflow is:
Aperture: exposure, white balance, spot/patch & cropping (90% of the time this will suffice and there is no need to go onto Photoshop)
If the image requires it, I then go into CS2, and a typical workflow would be:
initial sharpen, Velvia plug in, Noise Ninja, save TIFF -> sharpen, convert to 8bit, convert to JPEG.
I like to keep a JPEG available for speed more than anything, as working with several 70mb+ TIFF files at any one time can be a bit of a chore.
A <7mb JPEG on the other hand is relatively easy to churn through.
Thank you for the advice, it's much appreciated.
Incidentally, I find Aperture exceedingly slow, even with a relatively small library.
Do you mind if I ask how large your library is?