i use 2, chrome and explorer.
Let me tell you why, some sites are really hard to do on chrome , takes minutes to get the timer going, and that same problem is with explorer, so i switch a lot. Sites that don't work on chrome work great on explorer and visa versa
Got them open at the same time and that works great.
Chrome is faster and explorer give me a lot of frame freezers.
Maybe i will try firefox one day, they say its better dan chrome.
greetz