a quick and easy add-on to Firefox runs the IE engine to render the pages you "need" IE for. You can set it up to always load certain pages and/or sites. I haven't opened IE itself in years.

For instance, within Netflix.com, I have it set just to render the streaming player, because it won't run in Firefox. Everything else on that domain gets rendered in firefox. You can set it to either open a new tab or stay on the current tab as it changes. An Icon in the bottom right firefox tray can be clicked to switch back and forth, if you get to a site where it doesn't render and you were expecting it to.