After using the Shazam Encore app I was pretty impressed.  Shazam found almost every song I tested off of the radio, mostly getting stumped on remixes of songs.  After testing SoundHound I can say without a doubt that it is better than Shazam in every aspect.  SoundHound claimed that it can recognize songs in as little as 4 seconds so I put this to the test.  For the most part songs took a bit longer to recognize, probably on average about 10 seconds for an average song on the radio.  I was able to identify a few songs in the 4 seconds that SoundHound claimed, usually if you're playing the chorus or some part of the song that stands apart from other songs.  I liked how you can cut off the recognition process at any time and have SoundHound evaluate just what was played up until that point.  This would be useful for ID'ing a short part of a song in a commercial for example, where the song clip would not last the full 30 seconds a song may take to identify. 

Once you ID a song it doesn't end there.  You have the option of purchasing many songs or ringtones off of iTunes.  If lyrics are available they will be shown.  If not you can Google the lyrics with the touch of a button.  Any related YouTube videos will be viewable and you can share this newly found song via the usual social networking outlets.  If the artist is touring you can find all tour dates and locations as well as purchase a ticket to their concert.  All positively ID'd songs are logged in a history along with a Google map location of where you were when the song was identified. 

If all of these options were not enough, SoundHound offers one feature that no other music recognition program has ever offered, and that is the ability to ID a song by singing or humming.  This feature works with astounding accuracy.  SoundHound's features go well above what any other music recognition app currently offers and should be the only app considered.