I saw this video a while back and was torn. I was torn between feeling like this was kind of lame or very inventive. The more I watched it the more I thought it was pretty cool that they could sound this good a cappella on a subway (besides, it's a great song too). This is another strong example of a good (and cheap) viral video. With over 600,000 views these guys have probably found a broader audience than they would have otherwise had, particularly in the U.S.
Link for feed readers.