New 2007 file extensions

So, has anyone out there noticed the new snappy Microsoft file extensions on the end of Office 2007 documents? Word went from .doc to .docx, Access from .mdb to .accdb, PowerPoint went from .ppt to pptx, and so on. I don't like that it is different, because it is well, in a word, different. Change is hard. I do like that it differentiates Microsoft's new XML-driven files from the older non-XML format. Oh, and I love how speedy stuff is. Office 2007 seems to load the screen faster than 2003 or 2000 did, which is nice. I wonder if these file extensions and the XML foundation will amount to great XHTML validation for converted docx? It would be nice, especially since the web has been a bigger focus for Microsoft in recent years. It is a little hard to get used to the 4-5 character file extensions, but they are MORE descriptive, which helps. Here again though, I don't think it cuts down on user confusion, but perhaps Microsoft thought it was a necessary move to ensure future non-confusion and compatibility. Other than that, the X on the end is just plain cool! Sorry, get out your Kodak, I think I just had a geek moment.

You would have thought that they'd just keep the extension the same?
I can't see any 'technical' issues as to why this couldn't work, this reminds me of microsoft's new card space file extension - they call it .crds - why not just .cards

I personally like .docx not be able to run macros. It's much more secure as you KNOW wheter you're opening a potential threat to your computer.
XML also makes easier to write programs to manage Office documents.