I'm not going to provide much commentary, because I want you to read the articles I've linked to and come up with your own conclusions. The only thing I will say, is that I am not a fan of the catapult. Feel free to make your comments and thoughts below.
The first article: "Pulling Technique in Weightlifting: The Tripple Extension vs. The Flatfooted/catapult".
The second article: "Weightlifting Mechanics vs. Weightlifting Technique: The Science and Art of Coaching and the State of US Weightlifting"
I also wanted to link to a website that holds all the publications and research done by Dr. John Garhammer. John has done all the biomechanical and scientific research on the snatch and clean & jerk in the US.
Feel free to troll the Pendley Forum, where most of this debate has been fostered and developed as well. It's worth the time. ;)
Lastly, I leave you with this quote: "You can have your own opinion, but you don't get to have your own facts." -Unknown