I've worked with a big CDN before, its expensive and a bit of a pain. But it they work, oh hell do they work. If you want to get content to Asia in a 1/3rd of the time then its the way forward. But your going to pay for it so you'd better be making a load of cash.
I discovered this nice company today CloudFlare, basically a CND for small sites. There are some added security features as well but its the CDN thats interesting.