DDOS is part of life on the Net :-(
It actually happens daily to us multiple times, but most are targetted towards a single server and only like 10MBPS. That is not enough for clients to even notice, except on the box it is directed to. This occassion was different however, as they were coming at us with over near the same capacity of our entire network! This was a highly planned attack, by individual(s) with alot of resources. We'll be investigating and dealing with it legally.
All I can say is that after the network issues earlier this year, we spared no expense hiring a new network engineer, and simply looked for the best. Considering the scale of this attack, and the speedy resolution, he just earned his paychecks :-)