My basic objection is that it's less an application for what I want to do than a storefront for what they want to sell me. I prefer to have my stores and my applications more separate. If I want to buy something, I'll buy something. If I want to listen to something, I'll listen to it. It bugs me to mix the two. My personal preference.
For others' objections, see here.
Here's a paired down list from the link -
It’s a store, stupid
The library manager is prehistoric
No web browser/Wikipedia/anything
No plug-in architecture
Massive memory footprint
No support for other music formats Ogg/FLAC/etc.
Drag and Drop sucks
Bloatware downloads
Can’t use iPod as a music transport with iTunes
iTunes is slow
I've been an itunes user since iTunes 1, before there even was a Windows version when i had to use Windows Media Player for all files that weren't MP3 and, I can't even remember the name of the old windows jukebox* I used to use, it was good though an an MP3 player (Someone has to remember their first MP3 jukebox software... if you do, throw a name out because this is going to gnaw at me forever now), before there was an iTunes store, before there it had the capability to show images or play videos, and back when the store purchases all had DRM on them and you not only couldn't share music, but the music you purchased wouldn't work in other programs like iMovie.
Keep in mind the complaints in the linked article are about iTunes 7, which is an easy 5 years old now.
I'll try and put my comments on the bullet list and keep them brief.
The short version - the list is is like "well I don't like them, they wet their nests" quality complaints.
The long version- (all titles theirs)
It’s a store, stupid - if you don't want to see the store, don't click "iTunes store" in the lefthand pane.
The library manager is prehistoric - Baloney. This is a common argument from people who want iTunes to act like Windows Explorer. iTunes organizes by the id3 tags in the MP3 or MP4 files. The article uses iPhoto as an example of how this should work but fails to take into account that pictures taken from a camera have no copyright restrictions, no id3 tags with notes or details, and very little other information but dates and times and filenames.
No web browser/Wikipedia/anything - it's a software front end for a hardware music player (the iPod). Also, the world has browsers to type "radiohead" into whereupon they arrive at wikipedia or the band page, or wherever.
No plug-in architecture - To plug in what, exactly? The article doesn't give any examples other than the visualizer.
Massive memory footprint - not the case in many, MANY years.
No support for other music formats Ogg/FLAC/etc. - Non standardized formats. The format that the store uses is MP4 because of DRM restrictions demanded by the record companies that put music in the store to begin with, and that's based on MP3 format. MP3 is a standard created by Motion Picture Experts Group. Ogg is open source (not good when DRM is a requirement), same with Flac. Because changes to MPEG content require a standards release by the MPEG group, and because those standards make it possible for every device that plays MP3/MP4 format files to read the id tags and process the files the same way, also critically important for hardware devices to do the same thing. But building a device around a non-standard open source format is way too risky for commercial products.
Drag and Drop sucks - No it doesn't. Drag music files to the library or a playlist in the library and they appear in the library and the playlist. Who ads a track (or several) to more than one playlist at a time (another complaint in the bullet)? And for the two linux users who will tell me that's all they do with their library of Ogg files ripped from first press vinyl and categorized by descriptions of the band's combined pheromone signature at least seven times a day, then I agree that clearly iTunes is not the music manager you need.
Bloatware downloads - Baloney also. iTunes is built on Quicktime, no Quicktime no iTunes. Don't want Safari when you download iTunes? click the radio button that says "don't install Safari", it's not that hard, really.
Can’t use iPod as a music transport with iTunes - Or, "How Steve Jobs was able to create a digital music marketplace with the record companies support and songs sold for 99 cents each". iTunes is the software front end for the iPod, and today, for the iPods that don't have web or visual interfaces (shuffle/classic). The point being I can't take my library of 20 gigs to my friend's house and give him all of my music. It's difficult even to move the iTunes library around (believe me, I've deleted one by mistake by not following the, I think, purposefully archaic instructions) so it's hard to copy your library to a removable disk, and you can't make two copies as far as I can tell, of your library.
iTunes is slow - the example in the article asks us to imagine a 200 gig iTunes music library. Seriously? I mean, i can imagine one, and with video and movies and TV shows in HD yeah, sure, I guess. But what's fast? click on a file, it begins playing, are we talking seconds of loading time, or milliseconds of lag in frame refreshes, or what? There's nothing in this comment that suggests slowness.
So there, that and a buck fifty three will get you a small Dunkin' Donuts coffee.
*ON EDIT - WINAMP! That was my the MP3 player I used on my windows machine. Jeez that took forever to remember...