>Well, for the few times I use IE, I find it just as simple to open a separate IE instance (leaving FF up) and just alt-tabbing between them.
>
>I generally try to run with as few layers of software as necessary - so why run IE in an FF tab, when you can run it directly?

For me? Convenience.
Many times I was forgetting an opening an MS link in FF and finding problems, then remembering I have to fire up IE, keep a second set of favorites there, and maybe passwords and cookies. Much easier to have all in one.