It targets muscles that just don't get targeted with weights (like the saddlebag area)- not that you can "spot reduce", but it's nice to work all the muscles from different angles. A lot of it is bodyweight, too as well as some actual weights. For most people, it delivers much faster results. I don't know why, but it does.
They use light weights in a way that makes you feel like your arms are going to fall off, lol! I'm actually developing my arms faster w/ Bar than I was with kettlebells and heavier weights (esp. my triceps!) My arms are more cut than they've ever been and I've only been doing it for about 6 weeks. I'm too lazy to waste my time with things that take forever to get results. That's why I like Bar (and related systems like Lotte Berk, Physique 57, Core Fusion, etc).