It's a large DDoS.
You sure its not just the thousands of Filipinos and Indonesians logging on for their sig shift?
On a serious note, do you have any stats on where the traffic comes from to this site? Would be interesting to see.
.Today was to only day I experienced problems loading the site. Sometimes it just didn't load at all or took a while to load up. But if I tried multiple times I sometimes got through, that would comfirm it was a ddos attack at the time. I've never experienced a ddos on here, but as long as the servers are fine I am not too worried about it.
When I'm writing this everything is back to normal.