Maybe I'm being a capitalist pig here but I think using open source software in office is really unprofessional unless said office is the IT.
Unprofessional is wasting money when you could
not be. A company probably
should have one computer with microsoft office products on it, just to ensure compatibility in the face of MS's horrifically toxic business practices (.docx bullshit, the upcoming compatibility breaking extension change, etc.), but considering how functional LO is these days going with it is the business minded individual's choice.
If there were a notable functionality difference -- and speaking as someone that has been working back and forth pretty intensively with both LO and MS office the last year or so, there
isn't -- then there'd be reason to go with MS over open source stuff. As is, the only unprofessional act would be complaining about minor interface differences and the occasional compatibility hiccup in the face of saving the company hundreds -- quite possibly
thousands -- of dollars in software costs.
There's plenty of people that hold that something is better (more professional, in this case) just because it's paid for, even if it's functionally identically -- and, in some cases
worse -- than something that's free. We call those people goddamn idiots. Professionalism is a methodology, not a price tag, and it's a methodology that, in the business world,
strongly includes efficiency in regards to composition. If FOSS can do the job, you use bloody FOSS and stop wasting the company dollar.