I'm not sure what can be brought to Winamp that'll make it better through open source. Maybe it'll be a default alternative for Linux distros? That'd be cool.
But, Winamp to me is just a program I use that plays video game soundtracks that are different formats aren't MP3 or WAV. Like Super Nintendo with .SPC for example.
AIMP has predominantly taken the mantle on my system as default media player, it's just feature rich and long won me over the day my PC suddenly rebooted and the song I was playing was just on pause with that program! Winamp couldn't do this, whenever I re-opened it, song stopped playing entirely, gotta play it again.