Muscle ups

Today's WOD..30 muscle ups for time.
What's a muscle up?
http://www.youtube.com/watch?v=JgetCXNhac4&feature=related
and from how easy that guy did it, I really doubt it was his first.
Tried to do one for about 15 minutes, but never can get the transition from pull up to the bottom of the dip position. Need to add this to my list of goals. After trying what appears to be a pretty simple maneuver, I have an even greater respect for gymnasts who can do completely sick routines on those things.
The substitution workout is 4 pullups and 4 dips for each muscle up (120/120).