I use both Chrome and IE. Microsoft have made considerable strides since the dark days of IE6 to become far more standards compliant (they still have some way to go), but I don't consider it a joke: If you're working in big corporates, IE is still the standard if the desktop is Windows. One of the reasons is that it works very well with Active Directory enabling single sign-on to intranet apps.
I really like FreeNas. But if you want to increase penetration of both the FreeNas product and (more importantly for IXsystems I guess) TrueNas into corporates, making the web interface IE compatible is important - after all, many corporates will not let users install a browser of their choice. Why place an impediment in the way of customers who really do have the big bucks?