Simply having fast app startup times doesn't not solve the problem. For example, very often I will want to quickly check my email or chat session while a page

Simply having fast app startup times doesn't not solve the problem. For example, very often I will want to quickly check my email or chat session while a page is loading, but if it stops loading that page when I switch applications I don't gain that benefit. I also like to have chat sessions open and get small notifications (usually a sound or on-screen indicator) when I have new messages even if I'm in the middle of reading a large article in my browser. Without background applications, neither of these usage scenarios is viable. It is this sort of usage that sets it apart from a general-purpose computing device and makes it into an appliance for me.