So, you don't state any of the needs your user will have, yet you ask if you will face any problems.
As I see things, if your users are satisfied with OO, then you are too. But we can't guess here. Knowing their exact needs when it comes to portability seems essential to me.
Other problems as the difference between button layouts in OO and Msoffice may be more or less important depending on the user base.
Let me finish by saying that for someone that doen't like the idea of "being stuck in microsoftland", you seem pretty badly informed when it comes to free/open source software.
A look at the features of open office would have answered at least the first and last of your questions.