Anti-aliasing on text?

Recently I have run into an issue surrounding text on my site.

Anti-aliasing on the main text at the top of the page (basically the title) is non-existent. This is really confusing me as when I go to Automattic.com and look at the main, large, slogan text in the centre I can clearly see it has been anti-aliased. When I right click and go to Inspect Element (in Chrome) it shows all the CSS applying to it, most importantly the snippet:

Now I'm so sure about the second rule but the first would certainly imply that it's giving the text the effect. The odd thing is when I go to ATO>Add CSS/HTML Snippets and add a class with that style in it and apply to the main title text nothing of the sort happens. I've heard it's to do with the size of the font, but even with the size set to 400pt or something it still looks pretty nasty. The styles are also definitely applied to the A tag though as any other style I add (e.g. text-color) clearly comes through.

Any help appreciated.

-Dapizz

PS: I'd prefer if possible to stay clear of the text to Flash converter thing (is it sIFR?) if possible.