Judging from your "I think it's awesome", this is another of those "agree with me or I'll get e-bitchy" threads rather than a genuine question.
Nevertheless, I'd caution against using it for the simple reason that you'll be developing a different motor pattern from your natural, unweighted one that could actually make your running less efficient. IMO, you'd be better off focusing on regular speed and endurance training (or maybe some drills in your lacrosse gear).