It's.... OK.
Very sluggish, awkward interface. Mostly stable. For basic Office compatibility, it's (of course) better than the cool but very basic .doc abilities of Panther TextEdit, about the same or better as AppleWorks, and not as good as the real thing. But for basic documents I find it generally it works pretty decently.
Personally, I find it acceptable as a tool to occasionally open, view, and make light edits to Word and Excel documents, but not acceptable for daily actual use.
I'd at least hold out until MWSF to see if Apple announces its long-anticipated AW replacement.