I think that everyone of us will be excited to test the future Internet Explorer 7 under Windows XP, but after reading this post on the IE Team Blog I'm a little worried.
The Team say that "We’ll post an updated pre-release build of IE7 for Windows XP publicly – no MSDN membership required – during the first calendar quarter of 2006.". 
So? We can't have a beta version to test until March 2006? This is not a good news for everyone involved on developing websites. Why all this time to release it?
At this time I think that the IE Team could do a big favour to the community: please release a document where you explain us all the conditions to build a IE7-compliant website. We can't wait this spring to know if our websites will be ok with the last IE version I think...