I've followed this specific brand/technology for a while and it's definetly going to be the armor for the US military in just a few years. Downside? Price of course.

Advantages - you can wear it over more than just your chest - arms, legs, etc can be protected by a cloth-like-flexible material 15 TIMES stronger than steel.

FOXNews.com - U.S. & World - Military Testing Improved Body Armor