Many of the web developers whom I met recently expressed thier main concern on Internet Exporer 7 as "Change in User Agent String"...If you wonder what the heck is that.. Read more about "User Agent String"

IE 7 team is proactively collecting very good feedback from developers and documenting the details on all the issues/concerns. That's a very good way to talk to developers in thier language. They have recently blogged a nice post on User Agent String issues in IE 7 and related documentation here.