runkel,
While there are problems that can arise form using USB 1.1, they are usually slower transfer, and having to do part of the transfer at a time, i.e. smaller playlist at a time.
Some USB 2.0 addon cards introduce their own sets of issues.
iTunes system requirements call for a 500mhz or faster processor, and do you already have Mac OS X 10.4.10 installed?
Hope this helps,
Nathan C.