OSX comes bundled with iTunes so I thought I'd try it out and my official verdict is this: It's awesome. In the Windows world iTunes sucks mostly because it's such a memory hog and I can totally understand why anyone would hate using this in XP. On the Mac you can use it how it's meant to be used.
I've used many MP3 players over the years including MusicMatch, Windows Media Player and so on. In XP my main player was an old version of WinAMP (version 2.81). It's small, fast and works well.
On the Mac I decided to try something totally different and made use of MP3 tags instead of finding what I wanted to by file name and folder (which is how I used to do it). The interface is extremely clean and now I have all my MP3's organized with searchable tags. It makes management of all this audio and music a helluva lot easier and I'm totally impressed by it.
In the past I never used MP3 tags because to be honest using playlists was a chore. Windows Media Player wanted to convert everything to its "native" format of WMA or WMV which I didn't like. Other players just sucked up way too much memory and added a lot of unnecessary crap that did nothing but slow down my computer. My solution was just not to use playlists at all and rely on filename/folder instead. iTunes actually runs quite well in the background and is minimal on memory resources. I also finally have a way to edit tags EASILY while still keeping the MP3 "as is" without changing bitrate or format. I made use of editing multiple MP3's at once quite often (such as mass-changing "genres").
Additionally, iTunes doesn't throw any unnecessary eye candy your way. For some strange stupid reason a lot of MP3 players try to dazzle you with 3D graphics and make all the text really tiny and hard to read. The iTunes interface is clean and everything is easy to get to. And I can read it; that's important.
One more thing - iTunes has volume normalization that actually works to my liking, and that's a big deal because I usually hate software that screws with the audio in any way. iTunes calls it "Sound Check". What it does it make all MP3's play at the same volume. This is very good when you have some songs that are louder or softer than others. The coolest part is that you can turn it on or off easily.
So yeah, I like this software a lot.