You can actually open up documents in other places like Dropbox by using the "Open In" facility. You just can't save them to other locations other than Microsoft OneDrive. They will hopefully add other services in the future.
downloading is not the same as paying for it ...
I also downloaded it to give it a try, just to see what they came up with. But actually, you can't do anything with it without paying. Officially you can 'read' documents, but only if you have the microsoft drive (or however they call it) - there are no other ways of getting documents in there. I know I can only read, but sort of was hoping to have some decent ways of getting documents in there to read.
So yes, I downloaded, found out that not usable (even for a quick try out) and deleted.
To bad they don't have a measure for the most deleted app .....