Most Linux distributions have moved or are moving to LibreOffice. I've been using it (Writer, Calc & Base) for 9 months now and there are a few significant improvements over OpenOffice. It's certainly quicker loading and seems snappier in use.

The main reason to switch is that LibreOffice is the one under active development - OpenOffice is dropping behind and losing users. I'm finding that a number of colleagues who are still on Windows are also switching from Microsoft Office, which makes exchanging files so much easier.

I should mention that I've never used Microsoft Office - I moved straight from Lotus Smartsuite to OpenOffice.

Phil