IE7 has finally been released! So I'm a bit late. Personally, I'm happy for a new IE, but, professionally, it's just going to be a pain. Since you can't have side-by-side IE versions (not easily anyhow, but other browsers are the same way) it is difficult to build and test websites for IE6 and IE7.
I did install one of the IE7 betas in a virtual machine to test the web applications I have built and support. None of them had any issues which was encouraging.
I am a little surprised at the significant GUI changes Microsoft has decided to make for IE and the Office Suite. But I suppose it's not all that different than introducing the "Start Bar" in Windows 95/NT but change is hard.
I'm not a user interface expert but I believe that a consistent location is more important than "good" design. This is why Microsoft has a standard for Menus and Toolbars. You'll notice that the File, Edit and Help menus are almost identical in every program. The order of toolbar buttons is almost the same in every program and they are almost always in the same place.
While playing with IE7 I found myself moving the cursor up toward the 'Tools' menu to make configuration changes but it's not where it used to be. This makes for a slightly jarring transition. We seem to understand the idea of consistency between applications and webpages. Overall, I think these GUI changes are improvements and will make the browser's features easier to access. Hopefully these changes are leading toward making it so application functionality can more easily be discovered.
For example, I suck at MS Word. I can write a letter, change the font size, make it bold and so on. I can't make a table of contents that will auto-update the page numbers to match my chapters. I know it can be done because I've seen it. I've looked through the menus and some help but couldn't figure it out. The GUI does not lend itself to discovering this functionality. So I have the common Table of Contents that I have to constantly update, doesn't quite line up, and has the funny ........ with some converted to (...).