A study published by the Norwegian "Direktoratet for forvaltning og IKT" (Agency for public adminstration and ICT) comes to the result that OOXML is not suitable for being used by the Norwegian government. The study is available online in Norwegian. Amongst the reasons that are given are that the standard with its more than 6000 pages is not appropriate; it is not suitable for collaboration; and there is only one software that can implement it and produce the respective file format. Norway recommends pdf for electronic document exchange of documents that don't need to be edited and ODF (open document format) for all other documents.
See, for instance, the reports on Heise online (German), CIO and on Computerworld.