You have hit the nail on the head.
I work for a small company where we recently considered moving to Linux on our workstations. The Operating System was not an issue, but the cost of retraining our staff to use OpenOffice out-weighed any benefit we might gain. Taking even half a day to train a busy executive would cost the company more in lost time and productivity than we could ever hope to gain in savings through licencing costs.
Meanwhile at home I have switched to OSX without any drop in productivity (well apart from time wasted playing with all the pretty widgets) because I can use Word with no time spent relearning the system. Someday I will try iWork but I am just too busy right now.
Microsoft may create a version of Office for Linux, but it will be after they have lost the battle for the desktop not before.
"Everything should be made as simple as possible, but not simpler." -- Albert Einstein