There's really only one thing which sets openoffice apart from microsoft office, and that is it's FREE!!!!
Link here:
OpenOfficeBut openoffice does a great great job, and is all open source. It provides quite a high level of compatibility with Microsoft Office, being able to both open and save into Office format.
Obviously that works wonders then with third party programs like Ovation. Because you can export from Impress to a .ppt file, Ovation doesn't seem to know any different!
It would be great if you could integrate Ovation with Impress like we can with PowerPoint but I guess that would be quite a big development step.