Then you missed the best bit.
I don't think it's messy, it's a drum comp piece and therefore he changes tempo and beat a couple of times in order to show his skills. Mangini is a session drummer and plays with all the big names when he gets the time. Listen to some of his in-band stuff if you want something with a consistent beat all the way through.
Looks good to the eye, but I can't hear what he's playing, got another one with better audio?