My work has rolled out IE 7 across the whole workstation network, don't know about servers.
I am running IE8 beta on my machine, though. None of the internal systems seem to be affected but some secure sites, i.e. internet banking kick you out when using IE8. Fortunately, there is an IE7 compat mode.
I use IE 7 at home but when I connect to the work exchange server it crashes when I hit the send button!