I rarely use Microsoft Internet Explorer, but I realize that lots of other people do, so I usually try to support it as much as is practical.
When I checked the newest version of PhunkyBB with MSIE tonight, it really looked terrible. Thankfully it only took a few hours to get everything pretty much in order.
I've been testing on an Asus eee PC with MSIE 6.0, which obviously isn't the most common MSIE setup, but it is a good test bed because of its screen size constraints.
I also have a more recent version of XP with IE 7 on a fifteen inch laptop screen. That is a much more common setup, and I'm hopeful that it will work from the start of testing.