Windows Mobile has not had the ability to handle OOXML-based documents until now.
This might make 2 applications which are built from the same codebase and properly support a derivate of OOXML. Both applications come from the same company, to whom OOXML is "a simple matter of (its) commercial interests", according to its own manager.
"If you're doing something hard and nobody hates it, you probably aren't doing it. If the right people hate it and those people happen to be some of the worst people alive, so much the better."