Considering I use less than 20% of the available features it makes no real difference to me which program I use. They both work equally well as far as I concerned, especially as Openoffice has come a long way and gotten rid of most of the obvious annoying bugs. The fact that Openoffice is free of course makes it my first choice when installing on other people's computers.
My personal opinion, I like OpenOffice 2.0 better. Office has served me well in the previous years, but it takes up way too much space. Office 2003 took up over 600MB of my drive. OpenOffice only took up a little over 200MB. Plus, I really don't need InfoPath. I mean, it's just really dumb.
well in my experience there hasn't been much difference between the two but i prefer openoffice since not only it is free but handles document processing well aside from the fact that it has also lots of support. the only thing that i noticed is that the formatting on one program (MS office) when exported to the other (open office) varies in formatting.