I don't know what kind of a "power user" you are, but Office runs
horrendously on my new 20" alum iMac, even with an extra gig of memory installed. I find this especially ridiculous since both the machine and the OS were available for testing for months before Office 2008 was released.
In my experience, Office 2008 behaves
literally like bad beta software.
It takes forever to start one of the applications and then a further five to ten seconds for the graphics to settle down so that clicking on the tabs actually works. There are copious screen re-draw problems, and all graphics transitions pause before they fire. You can't even move an active window across the screen without getting a one second freeze in the application. It acts almost as if it's working over the network on a thin client or some such.
If there are users that *can* use Office in any reasonable way, I can only assume that MBU just didn't test it on all graphics chips or something. On my machine it performs so badly I find it hard to believe anyone that says it's useable at all.
I don't use/need it myself and am currently advising everyone at my place of work to avoid it. This even though our University has a blanket license making it free for anyone who wants a copy. How bad is a piece of software when you can't
give it away?