Matthew Ryan contends that "The little things mean everything..." and Bush (the band not the President) said "It's the little things that kill." When it comes to iTunes 7.3, it's the little things that have me annoyed. First off, everything works, so it's not a matter of losing functionality. One of the little things that changed was the way it handles the alphabetization of bands that have a number to begin their name (i.e. 10,000 Maniacs, .38 Special) which isn't a big deal, just took some getting used to seeing A-ha at the top of my music.
I use eMusic. When I download music from eMusic, I have to add it to my iTunes library by clicking File>Add Folder to Library. In the past it would remember what folder I'd previously added and take me straight there. Now it "forgets" and starts me in the 'My Music' folder which I don't use for storing music, it's rather tedious to drill around to my external hard drive to the eMusic folder.
I've been listening to my iPod while it's plugged into my computer at work since moving into a new office. Everytime I plug in my iPod I'm taken to what I can only assume is a default for the iPod in respect to the columns it displays. The default includes Play Count, My Rating, and Last Played which are all features I don't use. Not included are track number, year. Each time I "customize" it the way I want it to be, but the next time I start it's all back to the default.
My understanding was that the upgrade was due to the iPhone, but I not only find the changes impacting me to be unrelated to anything specific about the iPhone, but as Matthew Ryan and Bush say, it's the little things.