They will see the IE8 tour, which is not even a popup. It runs within gthe browser, and by far most new IE8 users, are very happy to see that IE8 tour, because they are not techies, and IE8 instructs them, in a very friedly way, on how to use IE8
The dialog that offers to show you the tour pops up in front of IE8, it IS a popup dialog. And no sorry but nobody is ever happy to see any application tour.