Firefox is by far better the IE8, but I still use Chrome and IE8 as well. Each has their strengths and weaknesses. Chrome is the fastest with the fewest problems, but it also has the fewest plugins, plus there is some functionality that I don't get in Chrome that I like better in Firefox.
When I need to use IE8, I use a plugin for firefox called IE Tab Plus. It lets you open an IE8 window inside of a firefox tab. Sweet!