I used OpenOffice for a bit, but it eats up Word documents and spits them out in a way that does not usually successfully convert back to Word. So if you are going to be using Word, ever, don’t use OpenOffice. Just stay in Word format.
If you can make the break completely from Word, then I would say OpenOffice is fine. It has trouble with passwords on Word documents, so if you use them, you may have to decrypt them in Word before you convert them. I’m not sure it has the capability of putting passwords on documents.
I’ve found that switching word processing software is always a pain. OpenOffice does things differently, and I’d rather not have to relearn everything, as I have already done several times in my life. I went from WordStar to WordPerfect to Word, and I’d rather not have to go to OpenOffice. Since I can get academic pricing on Office, I don’t really want to switch.
But if you are going to switch and stay switched, I think it is probably a fine piece of software. I doubt if it does everything Word does, but if you don’t don’t need all the bells and whistles, you should be fine. But if you have to do academic or legal word processing, I would be careful to make sure that footnote software and other specialized things work with OpenOffice.