I've been using Office 2007 for almost three years now. I was extremely prfficient in all versions up until 2003 because they developed and improved organically.
I still struggle to do things on Office 2007 and save all my files without the "x" in the file extension because I often go back to 2003 to do things quickly.
This isn't because I'm a Luddite, it's because Office '07 is rubbish.