I noticed one problem with IE8 text rendering with Dynamic HTML content. I was actually updating my status in Facebook.using my IE8 RC1 version under Windows XP. As you can see in the image the existing contents were rendered using cleartype font and the new text added to the page with standard rendering type(even the clear type is enabled). See the image below

I also tried this operation with Firefox but it doesn’t have any problems. Seems rendering issues with IE8. The existing text is marked in blue rectangle and newly added one using red. (I know the above image is crappy. Just click on it and see the original image in new window)