One of the problably most discussed features is “InPrivate”, sarcastically baptised the “porn mode” due to is most striking operation field. But this function is simply an automatism for a standart procedure, which are already offered by several other competitors on the browser market, i.e. “Clear private data” function in Firefox.
By concealing the browsing behavior and thus avoiding the data mining by webpages, this function cuts off targeted advertising, which will not be appreciated by the marketing companies.

So this measure will be welcomed by the data privacy protectors, but certainly not by the greatest online advertiser, namely Google, who has by the lately swallowed DoubleClick for $3.1 billion, who are specialised in targeted marketing.

Hopefully the MS software engineers had been sticking a little bit closer to the standarts defined by the W3 consortium.

On the download page itself M$ only gives common talk:

Internet Explorer 8 is the latest version of the familiar web browser you are most comfortable using, helping you get everything you want from the web faster, easier, more privately and securely than ever before.

• Faster Internet Explorer 8 is more responsive with new pages and tabs, opening up fast and reliably. You can now get to the information you care about most, in fewer steps; one click access to your webmail, favorite news sites or other online services.
• Easier Reduce the steps to accomplish many common tasks, and automate your access to real time information updates. You can keep track of your favorite sports team, news, weather with a single click.
• More Private Helps protect your privacy and confidential information where ever you go on the web.
• More Secure Helps protect and stop malicious software from reaching your PC, and makes it easier to detect when a website is an imposter.