I would have to say that, yes, there are some sacrifices you make. For instance, there is no built-in reading level analyzer in OpenOffice (OO). There is an add-on you can get, but it is sometimes a little buggy. It is possible to track changes and everything, though, so that isn’t a problem. You can add written comments to a paper, but as far as I know you cannot add audio comments.
Some things are not impossible in OO but seem a little more awkward to do. Page numbering is one of them. If you want the title page to not have a number or if you have pages with Roman numerals followed by regular numbering, it is a little complicated to do. I think, though, that if I did it more often, I would remember from one attempt to the next and not have to go to the forums looking for help.
That brings up one of the real advantages of OO and other open source tools is that there is a great community of users out there who have either already answered your question for someone else or will be willing to answer it for you if it hasn’t come up yet. (I have never yet had a question for which I couldn’t find the answer on the OO forum.)
The only other problem I have ever had is that sometimes when I open my OO .doc document in Word, the formatting is a little off. This can be frustrating. But I have had worse problems with using different versions of Word on computers in a computer lab.
For me, the advantages far outweigh the disadvantages, but not everyone would necessarily feel that way. But I go back to what I said last time: Download it and try it for two weeks and then decide.