iTunes is definitely another great player, I agree. It's probably the only one that compares to Winamp (that I know of). I think it comes down to personal preference between the two really. The Media Library of both iTunes and Winamp are very similar. The ability to sort, categorise, search, view album art, and play directly from the library is what I meant by excellent.
Winamp doesn't seem to have "Smart Playlists" by default (possibly plugins?). Winamp does have a Generate Playlist feature, that lets you select some music and then finds similar sounding tracks from your Media Library by analysing the wave form of your selection. I haven't really used that much, I prefer to rate my music and use the media library to generate playlists based on those ratings.
Personally I really love the Winamp "Shade" mode (that allows you to dock a tiny strip version of the player to an edge of your desktop), and the modular window support. Being able to move just the Playlist to my second monitor and keep the Media Library on my primary screen is great!
The interesting thing is that, iTunes and Winamp seem to be the two major players in desktop audio players currently, so it's really strange that Nullsoft would give up Winamp so easily.
