Five years ago I strongly criticized the OpenDocument standard for being critically incomplete for spreadsheets since it left out the syntax and semantics of formulas. As a consequence it was unusable as a basis for creating interoperable spreadsheets.
Off the record several ODF participants agreed. The explanation for the sorry state of the matter was that there was a heavy pressure for getting the ODF standard out of the door early. The people working on the text document part of the standard were not willing to wait for the spreadsheet part to be completed.
That was then and this is now. Five years have passed and there has been no relevant updates to the standard. However, one thing that has happened is that is that Microsoft started exporting ODF documents that highlight the problems I pointed out. ODF supporters cried foul when it turned out that those spreadsheets did not work with OpenOffice. In my humble opinion, those same loud ODF supporters should look for the primary culprit at the nearest mirror. You were warned; the problem was obvious for anyone dealing with programming language semantics; you did nothing.
So given the state of the standard, where does that leave ODF support in spreadsheets? Microsoft took the least-work approach and just exported formulas with their own (existing) syntax and semantics. Of course they knew that it would not play well with anyone else, but that was clearly not a priority in Redmond. Anyone else at this point realizes that ODF for spreadsheets is not defined by the standard, but by what part OpenOffice happens to implement. Just like XLS is whatever Excel says it is.
One implications is that ODF changes whenever OpenOffice does. For example, OpenOffice has changed formula syntax at least once — a change that broke Gnumeric’s import. If you follow that link, you can see that OpenOffice did precisely the same thing that Microsoft did: introduce a new formula namespace. Compare the reactions. For the record, in Gnumeric the work involved in supporting those two new namespaces were about the same.
For Gnumeric the situation remains that we will support ODF as any other spreadsheet file format. Until and unless the deficiencies are fixed, ODF is not suitable as the native format for Gnumeric or any other spreadsheet. (There are other known problems with ODF, but those are somewhat technical and not appropriate here.)
Note: I want to make clear that the above relates to spreadsheets only. I know of no serious problems with ODF and text documents, nor do I have reason to believe that are any.