Its due to all the flash and other dynamic content as well as advertisements (that often break the page, especially the hot topic list).
It is slow, if you run this in different browsers you can see a difference and it is definitely slower than other gaming sites as well.
I love this site which is why it is the only site where I actually see advertisements, but, it has always been plagued with latency issues due to the type of information ioi wants to display as well as its core userbase wants to view.
However, it would be good in the next interation to look at HTML5 and other options besides flash as well as fully testing in different browsers. Its really annoying to be on the gamrConnect page and have a ad not place right and cover half the hot topics list.