I have never had any trouble with this site. I hear others complain sometimes. I use a Mac as well (actually, I have several) and my typical browser is Camino, but sometimes I use Chrome or Firefox. I do keep flash disabled all of the time on all of my browsers. So if there is flash content, I just get a box with the flash logo in the center. If I decide I want to see the content (such as if somebody posts a video) then I can click on it to load that one object.
Next time the site is running slow, open a command prompt and try pinging it for a few minutes. See if you are getting any packet loss between you and the website. If so, try other websites and see if you also get the packet loss there.
There have been weird situations where a router deep in the cloud somewhere is having trouble but only affects traffic moving in a particular direction from a particular source.
Site is working fine from northern Colorado. But I am only at 5,000 feet in altitude.