The IE team has a blog.  Actually, they’ve had a blog since July 21 2004.  Shows how much I pay attention.  But there’s a post on IE7’s CSS position that’s well worth the read.

From the intro:

We understand that we are far from being done and we know we have still a lot of work ahead of us.  IE 7 is a stepping stone in our effort to improve our standards compliance (especially around CSS). As an example, in the platform we did not focus on any proprietary properties – though we may try out new features in the future using the official –ms- prefix, following the CSS extension mechanism. We also work very closely with the W3C CSS working group (which I am a member of) to help clarify assumptions in our implementation and drive clarifications into the spec. I really like to thank everyone who helped us here.

In all, we made over 200 behavior changes (bug fixes or new features) under strict mode to improve CSS2.1 compliance.  All this work (with the exception of transparent PNGs) has been done under the <!DOCTYPE> switch only, since all changes required behavioral updates to be more in line what the CSS spec specifies. To preserve application compatibility we will not make any behavioral changes to “quirks mode” as it has been established since IE6.