I think the thing that impresses me the most about The West Wing is the way they consistently pick really good music for all the episodes.
I mean the writing is fantastic (well, not so much this year, but in previous years anyway), the topics covered are always interesting, and the acting is great, but it still continues to impress me that they find such great music for each episode.
For the record, the music that prompted this blog entry was the Aimee Mann cover of "Shed A Little Light" (a James Taylor song) at the Rock the Vote concert in season 4.
Unfortunately, that particular recording of "Shed A Little Light" does not appear to be available anywhere, but the original was available at the iTunes Music Store.