@Laughing Man:

If you put it that way, then I'd have to say MS did a much better job doing (backward) compatibility testing between their MS Office releases than OO.o against MS Office formats =P It's so much less of an issue (format compatibility) upgrading to another MS Office version than to OO.o. Unfortunately.

As for user's response to the 'upgrade': Most will immediately understand that MS Office 2007 is an upgrade from whatever version they were using before (nice gui, whatnot) and they wouldn't mind spending their own time exploring it and getting themselves up to speed. They either 'don't care' or 'somewhat excited' with getting such upgrade.
While getting OO.o replacement is seen as something 'inferior' or 'different' and they generally don't react as positively to this change. "Oh, the company is saving some money at MY cost.. I've to use this inferior software that makes my job harder or less convenient".

Of course user's response is part of the migration preconditioning process... while a great majority of them probably wouldn't care if you tell them about 'opensauce', but telling them how the saving from this project may help the company stay afloat in this tough time should earn their sympathy..

In the end, OO.o is seen as an inferior product which is cheaper, but comes with some unnecessary risks.