I have been playing around a bit with Internet Explorer 7 Beta 2 and one of the first things that I noticed about it [other than the new UI] is that the fonts seem to render with ClearType. It was a bit of a shock because it was really subtle at first but now I really notice the difference. If you have IE7 Beta1 and goto http://news.bbc.co.uk
and then try it with Beta2 you will see exactly what I mean.
I also found a link on the IE Blog about what has changed [http://blogs.msdn.com/ie/archive/2006/02/03/524367.aspx