One of the MSDN Blogs is offering a few details of that next headache set to arrive for web developers - Internet Explorer 7. With all the current hacks and workarounds, when IE7 first arrives there will be many designers scrambling to see what it does to their sites, and how many of the hacks it now completely ruins.
http://blogs.msdn.com/ie/archive/2005/04/22/410963.aspx
Looks like we can expect alpha-transparency png support, and a few other annoying bugs to be ironed out. Beyond that? We'll have to wait and see.