Dithering....
you can't live with it, you can't live without it.
Bob writes some great articles on this mostly dry subject.
Whether you should dither while mixing or not really depends on what type of files you are using. If you are using 24 bit files, leave dithering alone until you have the mix done, then apply 16 bit dithering to the finale mix then do some kind of Save As and choose a 16 bit resolution.
If you are working with 16 bit files, or even 20 bit, you will probably want to dither while mixing.
Basically, dithering just add's a bit of noise to the audio at around -96dbfs. This noise allows the the least significant bit to stay on, so you fade outs sound much smoother. Any applied functions while mixing with software create errors to the digital data at the lowest volumes (this is being very simplistic really, it is a complicated deal really) and this can make your audio sound sort of grainy when the volume starts to get low. Oh screw it, just remember that if you are dealing with 24 bit source files, don't use it. If you are using 16 or 20 bit source files, use it. That is all you really need to know for know. Do go and read the excellent articles that Bob Katz has written on dithering though. After about 20 reads, you might actually retain some of it, or you may be smarter then I!
Good luck.
