A few things to note however:
1. It is unclear from the video what network was used for the test.
2. The Windows Phone 7 device is a prototype.
3. Mobile IE is not yet complete and the OS is not complete.
4. Most importantly, Engadget found that the browser was almost as fast as the iPhone 4's browser ("Loading the desktop version of Engadget was just a hair slower than an iPhone 4, and just as importantly, rendering new parts of the page as you scroll is plenty fast -- not instantaneous, but fast enough so that you never find yourself consciously waiting for it to catch up.") and Matt Miller's ZDNet video of his Windows Phone 7 prototype device shows that the Mobile IE browser is faster than billed.
So, what can we conclude from the video. Not much except that some sites will post just about anything to get views.