There is a VDub MP3 version hanging around. Also, you can attach a WAV header to the VBR MP3 and use a standard version of VDub. I don't think you can recompress the MP3 though without outputing it to a WAV first.
The biggest problem with VBR MP3s is that sometimes the encoders "wig out" and stretch or shrink the audio so it's a different length to the video.
(Forgot to mention I use BeSweet for the Azid/LAME part).
