Just stumbled upon a great new extension for Firefox, named IE Tab.  It performs the same function as one of my other favorite extensions, IE View, BUT it actually adds the IE window as a tab right inside Firefox!  It also allows you to add sites that will always open up in an IE Tab (for instance, I included msdn2.microsoft.com, which has had its share of problems if you're using anything other than IE, but to their credit, it does seem to be getting better :)...).

Very nice!  Now I *really* won't ever have to open up an IE window, even when developing intranet-based/IE-only web applications.  Sweet!