I do because that is the browser mandated by I.T. for institution-owned computers which includes my new Dell E5520 laptop (also mandated by I.T. -- I had no choice). I think I'm the only faculty member with administrative privileges to install other software on their machine. So I also have Chrome and Firefox. Really ridiculous mandate, I know. That and the fact that I.T. specked 32-bit Windows 7 on a 64-bit machine.