The updated UI in StarCraft 2 is no doubt a huge improvement on the original's, and once the controversy of this is stripped away, there is much to learn. Here is a short video introducing the mechanics of "Smart Casting".
Now, you may be thinking these are rarely useful in your games, but here is a shoutcast of a high level match between WhiteRa and Jinro, where the huge armies involved made knowledge of "Smart Casting" a key factor. What use is a large force if you can't utilise its abilites!
You are no doubt disgusted by my Commentating skills, but don't fear! Here are a few more replays we found scouring our Replays System, which showcase brilliant control of large armies, as well as being thoroughly entertaining!