It was amazing! I got there at 12 and there was already a small que, waited for 5 hours, and then Kojima and Yoji Shinkawa, the guy who does all the MGS artwork, appeared.
In the end they were only letting people get ONE ITEM signed each, which kind of sucked, but I guess it was to deter eBayers from selling a load of signed stuff on there, and to make sure as many people got seen as possible. So I got my FOX-HOUND GameCube and MGS Premium Pack signed (my friend got the PP done for me).
Here are some photos and a few videos at the bottom. I suggest you watch the vids, they're only about 6mb each:
http://homepage.ntlworld.com/j.brunner/MGS%20Signing/mgssigning01.MPG
http://homepage.ntlworld.com/j.brunner/MGS%20Signing/mgssigning02.MPG