Yes I have tried it through the Beta stages 1, & 2, and now finally RC1 (Release Candidate 1). Well apart from the obvious with the new layout and the tabbed browsing, IE7 does look promising but don't be fooled by its looks it does appear to be more stable than IE6 but it seems to be slower! But then that maybe be just me!
It does have some good features Integrated RSS Feeds that will work in sync with Microsoft Office 2007 Outlook.
Microsoft have done well and took notice of the surveys they did!
*Better Browser Controls
*Preview of Tabs in Quick Tabs (ctrl + Q)
*Favourites and history & RSS in one place neat!
It certainly is good rumors have it that it will come out as a Priority update via Windows Updates / Automatic Update!
My advice to most people is Just as FireFox has its downfalls IE7 is only just developed and not in final release as it is scheduled to go out with Vista so as to incorporate Windows Vista Online Site Protection restrictions and policies!
IE7 may not be compatible with 100% of the web!
My overall opinion is Good, Slick, but could be Slicker! ;-)