All these people saying it's so fast - have you tried it in full-screen mode?
That's how I usually use iTunes. I'm finding it awfully slow. Much worse than 10.7. Once I stick it in to windowed mode, performance improves a bit. But that's not how I like to use it.
I don't love or hate this new release. The 'up next' thing is long overdue, the UI in general is nice although it clearly needs more work. So there are some positives.
On the other hand, it's become much slower for me (RMBP). Also, the column track layout is very poorly thought out (e.g. it mixes disks in to the same columns). That's something I actually think Steve Jobs would have noticed; being a long-time music lover. Typically (going right back through CDs, cassettes and vinyl), "SIDE A" and "SIDE B" were shown in separate columns. (
example here).
If Apple had gone that route, the new iTunes layout would look beautiful and slide right in to music history. Right now it's just a sloppy mess.