IE 8 and dev tools

I just installed IE 8 on my machine. I also puuled up the dev tools. It seems we can use it to edit the code and see live results, like Firebug. It also seems like we can change how IE8 will render pages. If im understanding this, it says we can render pages in IE7 mode. If thats true, it can make debugging much easier!!
http://msdn.microsoft.com/en-us/library/dd565628(VS.85).aspx#html