Mufin for iTunes is a plug-in that recommends music based on your library and what you're listening to.
Unlike iTunes' modestly titled Genius, mufin for iTunes analyzes the content of your music rather than comparing your habits with other people's (I cannot be sure this is what Genius does, but that is how it appears). This means when mufin makes you a playlist it sounds quite unlike a Genius playlist, which makes pretty dull and predictable selections. Mufin for iTunes' playlists, to these ears at least, seem to fit together much better, without necessarily sticking to one genre.
Analyzing your library fully can be quite lengthy, as mufin looks at the music (tempo, structure, sounds etc), but if you can handle waiting, this needs only to be done once and the results will surprise you. You can choose the length, number of tracks or size of your playlist, and your playlist appears at the click of the button. I love making playlists, and was shocked by how good mufin can be, putting tracks together in ways that work, but I had never though of. Very clever stuff.
Another benefit of mufin, is it analyzes your music, so it doesn't matter if you have things that are not available on iTunes store, mufin will make a playlist from anything without sending your listening habits to anyone.
The recommendations are less impressive, we found some less mainstream tracks that mufin couldn't provide recommendations for. The recommendations it does give you are pretty good, even if there's no function to listen to them, except through iTunes store. Visually, mufin sits comfortably next to iTunes, and can be easily collapsed when it's not being used.
If you like the idea of automatic playlists, or use Genius, we think mufin will give you better results.