Thanks for the kind words. I try to keep each segment short - no more than a minute per piece - and at this point, everything I've got on the reel is from short film projects anyway.
A good way to maximize the effectiveness of your reel is to avoid showing the same shot twice. If you add an over the shoulder shot in one scene, then going back and showing that same shot again is just wasting the producer/director/whomever's time.
My reel is my calling card, and I've found that there's a lot of work that I've done that isn't representative of my style. Sometimes the work turns out a different way than originally planned because of logistical problems or whatever. I tend to shoot more contrasty stuff, but I also have a lot of really cartoony, high key stuff that I don't want people to see. The last two pieces on the reel differ from the first three, but I've grouped the scenes together in such a way to differentiate between styles, so as not to give the impression that I'm all over the place.
As I add more pieces to the reel, I may ditch the current format and just edit everything together to one piece of music, but a lot of the time it's hard to convey the right mood for two different scenes with one piece of music.