That's the argument? Not having windowed apps on a 10" screen? I was hoping for something a little grander.Then maybe you should get a real PC?
Just kidding.
The difference is that you can do real multitasking on a PC. I'm looking at my monitors and can see my Twitter lists, my IM contacts, my e-mail, my browser and I can quickly access my music library at the same time, without having to switch between them. Well, I do switch between the apps with my mouse, but I don't have to interrupt my work/browsing/movie watching when I'm doing it.
And that's why, my dear crack addict with a tag, I refuse to consider the iPad as a "PC" and why FS apps on the PC are BS.
A lot of what you're talking about is handled through notifications. I don't need my email and Twitter open at all times when I am alerted to new activity regardless of the open app. And again, the end result is the same. It's as easy for me to access the music player on my iPad as it is to call up iTunes on the dock.