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.
Backups are imperative, more so in an age of uncertainty, unpredictable weather, and worsening standards (quality of products going down while prices go up)