I've created a minify plugin for the js and css output.
It doesn't work for visionmedia/debug, because the require replacement is done after all plugins.

The origin source:

if ('undefined' == typeof window) {
  module.exports = require('./lib/debug');
} else {
  module.exports = require('visionmedia~debug@0.7.4/debug.js');
}

output:

module.exports=require("undefined"==typeof window?"./lib/debug":"./debug");

but in this case it would be better to do the minification for the whole output file not for each file.
But I guess there are maybe some cases to use something for each file.