I am new to all this so my workflow may or may not be the best...but it does work for me.
I always save my original RAW files (my Pentax K10D shoots in DNG) and when done processing in LR, export as "Processed RAW" in a seperate file. I'm not putting anything on the web, so the few that I feel are good enough to print go into CS3 as RAW files, for tweaking mostly using the suggestions in C2P. When done (sharpening last) I save into a "Print Ready" folder (with sub folders by the location and date of the shoot) using a flattened TIFF with LZW compression.
So, I always have my originals if I want to re-visit them in the LR RAW converter, the processed RAW if I want to try my luck again in CS3 and the best I have, soft proofed and ready for print in a third folder.
This may be more work then is necessary but with up to date software, it doesn't seem that either the TIFF or PSD should make a whole lot of difference, unless you're working in a specialized app like In Design. I've gone with TIFF based on Jeff Schewe's advice.
I hope this helps a little!
Phil