To those who worked hard on getting IE8 released on schedule, congratulations! In the same time we feel sorry to those who care about website compatibility, this means you have one more IE to hack on. Maybe this is the way how Microsoft helps to create jobs in the crisis, thanks!
Anyway here's some critics from my own opinion. Firstly it took over 15 minutes to upgrade my IE8 RC1 to IE8 with two restarts. If you haven't noticed IE8 by default is not backward compatible to its predecessors. A good example is the 'opacity' in css, to get your page displayed correctly in IE8 you need to.
Either in the <head> tag put,
<meta http-equiv="X-UA-Compatible" content="IE=EmulateIE7" />
or write something like this in the CSS,
However this may break PNG images with alpha channel from displaying properly. Yes, another PNG issue, :-<
Read more on Bb RealTech
If you want find out more about difference IE8 has to offer, please check out CSS3.info
Enjoy hacking another IE!