It was quite cool. I think it would be handy to use in tandem with a blog, since there are more formatting options and it is a bit more user friendly as far as adding pictures, etc. than the actual blog websites are.
However, I don't see web-based applications replacing software such as Microsoft Word anytime soon. People on slower internet connections would be at a major disadvantage. Also it seems that is would be easier to lose a document that you are working on due to the browser crashing (as mine often does) or other annoying glitches.