2. Are there any background processes I should shut down in order to get better audio performance?
yes: macosxhints and other sites offer how-tos for shutting down dashboard and even spotlight. both consume a lot of cpu and worst of all: they generate peaks in cpu usage. the other important thing is to quit mail.
3. Maybe this one's for a Mac list, but... My initial attempt at upgrading failed part way through due to unspecified errors. A second attempt went fine, even though it looks like 10.4 was half installed (Dashboard was showing etc). Is a clean install in order?
it is absolutely recommended to do a clean reinstall and not a delta upgrade. importing the old user worked nearly perfect for me.
lg
martin