Had a quick look and it's looking good, but I may ask for some thing, though.
1. Is there any reason, why it doesn't use Winamp's global playback settings for ReplayGain on 5.5x installs? It's a bit annoying, that you have to switch Winamp's RG settings off, especially since I'd use your plugin for video files only.
2. Are there any plans to make it localizable via the 5.5+ language system?