Just listen to the wonderful harmonies of this modified Christmas Carol. I've learned the lyrics and enjoy singing along. This commercial reminds me of the days my friends and I used to go to the mall/restaurants and serenade random people with our musical antics.
This commercial drives me nuts. I appreciate how the choir is made up of actual Best Buy employees that are doing their best, but the lyrics are a problem. Though there are no written rules, there are some definite do's and don'ts of lyric writing especially when rhymes are involved. For example, it's not a very good idea to rhyme face with mace. I know mace is most effective when applied to the face, but everyone makes this obvious connection. Unless you're going to do more with the lyrics and rhyme pushing the creative level past face-mace, I suggest exploring your diction space.
Likewise, "he's gonna have a cow" is another obvious line that should be avoided whenever possible. Also, it's better to use specific and descriptive words in place of generic ones like "thing." How about using screen? "When he sees this SCREEN!" After all, if you're talking about HDTV screens, then talk about HDTV screens.
And what do cows have to do with HDTVs anyway? They don't. It's...