Note that it will require a subscription to Office 365 for all features and will not have all the features (or even most from the sounds of it) of the desktop version.
My take on it:
I think it will be a nice app for those who already live in the Office 365 world and need/want a mobile window into that ecosystem.
It will probably be no better than the current offerings when it comes to being a stand alone app on the iPad. I will probably be nearly 100% MS Office compatible (with in the feature set), but offer fewer iPad native features than the more mature offerings like QuickOffice, Office HD, Documents to Go, Polaris Office, and the iWorks suite.
That's a guess, of course. We'll have to wait and see what actually happens.
{see how I snuck in those other Office like app options?}