I just downloaded the 8.1.1 version of iTunes without the previous 8.1 upgrade and now my music is skipping at irregular intervals. It ranges from about a half second to 2 seconds, and it almost feels like a buffering error or iTunes is getting distracted by otherthings I am doing.
It really sucks...and if it keeps it up I will start looking into other media players.
Here's something I found out a couple days ago that really sped up my iTunes: turn off live updating in the smart playlists you never use. Apparently, iTunes has to spend time updating all of them upon launch, so it opens faster for me now after I unticked all the "live updating" boxes.
Since I've downgraded to 8.02 I've noticed that 8.1 even with all the bugs and odd lag times, was a lot faster than the release I have now. But I think I'll be sticking with 8.02 until a new version comes out. I was successfully able to import all my playlists and music count totals when I downgraded, so I'm good to go.