You comment that IE8 was slightly faster than FF, but you don't mention which version of FF you were using.
The article is talking about the currently-RC-status 3.5. Were you, by chance, using FF2 or earlier to compare? Earlier versions of Firefox have known issues with memory leaks. Many of these, though not all, have been fixed in the 3.5 version.
If you're going to say that "IE8 is slightly faster than FF" and that it is significantly better on older machines, you really ought to have said which version of Firefox you were using.
Of course, this goes both ways. Saying Firefox 3.5 is lightyears ahead of IE, without mentioning which IE it was being compared with, is utterly useless. Yes, Firefox 3.5 is lightyears ahead of IE5, 5.5, 6, or earlier versions (if they even still exist), but not so much when compared to 7 or 8.
Anecdotal evidence really does need versions along with it to at least look intelligent.