Ok, sorry I don't think I was clear enough (and hopefully this doesn't come across as snarky, just trying to get to the point).
Yes I know that CSS3 is ignored by IE8 etc. etc. Yes I have a separate style sheet just for IE8 and below (in fact the stylesheet with the @fontface has been hidden from IE8 and below). If you have a look at the site you can see that within Firefox, the CSS3 font is show, but in IE8 it is just Arial that is showing (which is what I was going for). But that doesn't explain the weird blocky look to the bold text.
My style sheets are put in like this:
<!-- @fontface code -->
<!--[if !lt IE 9]><![IGNORE[--> <link rel="stylesheet" href="css/fonts.css?v=1.0"> <!--<![endif]-->
<!-- IE8 font code (just set to arial and bold) -->
<!--[if lt IE 9]><link rel="stylesheet" href="css/ie8-.css" type="text/css" media="screen" /><![endif]-->
Can you see the blocky text in IE8? Any idea what would cause such a thing?