Well I hoped this seminar, "Developing cutting-edge web applications with IE8" would be about new features web slices and activities in IE8. Well it wasn't. I should have read the description online..
My colleague Eric went to some IE8 seminars too so read his blog posts also if you want to learn more.
What was presented was that Microsoft likes Firebug and has implemented similar thing in IE8, now integrated into the browser.
Other New things in IE8 is that it supports Navigating an Ajax page, you have 10mb local data storage to improve performance and you can check if you're online or offline and save your data to name a few..