I love the iPods but, Jeez, iTunes frustrates the arse off me! As with many Apple products, if you don't like the way it looks or the way it works, you are stuffed.
When Genius first appeared, it seemed to be a useful addition. It's recently become complete bloatware, though, serving little purpose other than to hog all of my bandwidth whenever iTunes is open and attempting to sell me songs that I already own.
I've got nearly 12k tracks on iTunes (all legal, of course, mostly ripped from CDs) and Genius is "gathering information about my library" all the time that I have iTunes open. I'm reluctant to turn Genius off because it has turned up some forgotten gems and I keep thinking that it must be nearly finished.