Suffice the say, even though I am not an admirer of Windows in particular, I never had missing glyphs from fonts that use Chinese characters. This just seems sloppy for Mac OS X.
Oh, yeah, back to Open Office. My initial impression is that it seems a little sluggish, not as intuitive or robust as Word 2008. Still, it is very functional for basic word processing needs, which is impressive, especially given that it is free.
My final conclusion professionally, if there is opportunity to buy robust fonts on Mac OS X, then issues with missing glyphs should be resolved, otherwise, ugh, I would have to recommend, Windows. Ouch. For word processing, basic needs, OpenOffice is fine, more robust features, Office 2008 is good.