in my experience, they will marvel at the speed for a little while... until a favorite website doesn't display correctly for whatever reason. Then it becomes my job to play tech support.
On the other hand, we're getting to the point where some newer sites render poorly in IE, run very slowly, are missing features, or don't work at all. HTML5 and intensive JavaScript may be on the verge of reversing the old conventional wisdom about using IE for widest compatibility.
Irony at its finest