About the same speed i reckon. Much quicker than Firefox anyway.
Windows 8 is bit shocking, there is no startmenu anymore, but a startpage (part of the METRO interface used on Windows Phone7). They also supply Metro apps like IE (although IE also has the regular interface), weather app, alarm app, stocks app, etc.
The original 'desktop' is an 'app' as well, hard to explain. But there are a few vids on youtube that will explain it lots better
Basically Windows 8 is a combination of this video: