This is a really nice and useful plugin, but i do want to express one concern:
Right now there are 3 CSS files being loaded and 2 separate JS files. Neither of these files are minified.
When Usernoise is the only plugin you're using, it's not gonna make a drastic difference, but for someone like me who is using this among many other plugins, it really weighs down website. You can easily combine those 3 CSS files into 1 and minify it, and same for the JS files. You'd go from 5 requests, to 2 with a reduction in file size.
I mean.. usernoise-adminbar-css.css only has like 10 lines.. you can easily put those somewhere else and save us some load time.