Shouldn't the iPad be able to do all the things a computer can do? (rhetorical question)
No, they are different devices for different purposes. Those tablets simply don't have the processing and graphics power necessary to run large and complex applications. It will be a while until tablets can replace the personal computer.
Not exactly sure what you mean by "this" fast either. Nothing in that video was very fast compared to a newish computer. If web browsing is slow on your computer, there's either something wrong with your computer or internet connection. Chrome is lightning fast on my Thinkpad, even with 10 windows open.
In fact, right now I've got every Adobe program running, every MS Office program running, several chrome windows, several other large apps like Visual Studio and SQL server, and about 70 other processes that have nothing to do with these, and FS9 running on top of all of that, and my laptop can't even feel it (Far too many icons to fit across the W7 taskbar). This is why computers and laptops are necessary. Yours should be able to do it too.
You can get computers running pretty darn fast...