This single rocks! I, an obsessed and crazed Nirvana fan, own it as well every other CD they released and most of the singles and unreleased tracks. The three tracks found on the CD are awesome, as is expected from anything Nirvana.
Lithium, off of Nevermind, is probably one of the most well known Nirvana songs, and is amazing. The live version of Been a Son from the Seattle homecoming is also awesome. Been a Son is off of Incesticide, a released colection of covers and b-tracks, and is also one of my favorite Nirvana songs. Curmudgeon is, one again, amazing. It was never released on a full album, and can only be found either on this single or bootlegged off of other sites. It is slightly rawer and forshadows the feel of some of the tracks off of In Utero.
Overall, I give the single 5 stars. If you are a big Nirvana fan and don't have it, you're missing out. If you are just getting into Nirvana, or are interested in hearing more of their stuff, it's a great buy.
The single also has an added bonus. In addition to the three great songs, the sleeve contains a complete set of the lyrics to Nevermind. These are the lyrics as written by Kurt Cobain, not as interpreted by others who have posted lyrics on websites.
The Lithium single is awesome, and I highly recommend it.