I rarely get a really slow response but it does happen. One of the interesting things about using the Firefox browser is that it shows the various sites that are loading before a page finishes. With cable boradband, usually they go by so fast that they aren't noticed. But if there's any delay, they show up. At the bottom left of the window, where it normally shows the page that is loading or the word "done". I will see the phrase, "Waiting for x". Currently, the one I see most often when it slows down is, "Waiting for a.as-us.falkag.net" or something very close to that -- when I tried to see it long enough to get all the letters correct, it was running too quickly. Occasionally, when I see a slow response, the warning will be "Waiting for..." and then something to do with DoubleClick.
In other words, at least on my computer, it appears that slow responses are caused by delays in linking ads from other sites, not by anything in the forum software, itself. However, please don't take this as a complaint about the ads -- except for the JD ad, they are unobtrusive and often add another source of information to the site.