I've been using winamp for as long as I can remember as my primary music player when working at the computer, and I think sometimes people underestimate just how powerful it has become. Sure version 3 was a bit of a flop, but version 5 bypasses 3 totally, so if you feel like you were burnt back then upgrading from v2 to v3, it's completely different now! Personally, I like having a "player" interface, and a natural way of using my media.

I just wanted a simple way to load my ipod on any computer, without having to "pair it" or go through the bother of installing itunes, registering, etc - winamp lets me do this with its inbuilt ipod and portable media player support.

For example, to transfer an entire playlist in winamp to my ipod, I simply rightclick on the items I want and "Send to iPod", it queues them up, and hey presto, done. 
Another huge bonus, is that you can very easily download music from your iPod to -any- machine its connected to using winamp. As far as I understand, itunes doesn't allow you to do this, I can see why they do it for political reasons, but it really is an important function. You can also play / search / use your iPod while it's plugged in via the winamp interface.

Other cool things it can do, is autofill based in a query (which searches ID3 tags), sync local playlists, sync your media library, keep track of song ratings and transcoding!