I just came across OX Text™ (I kid you not about the TM... that's how it is on their heading) which looks really promising. Having a look at the preview though had me really excited. Like most of these applications, it requires a few too many clicks to get into a document. But once in, it looks like this:
Nothing to inspire any excitement except.... look to the right. They've separated Font and Paragraph formatting controls! (Finally, someone gets it).
The other really important feature for me is collaboration. I want to know that if I set up a document, I can share it with ANYONE and give editing rights to people whether they're with whatever service or not... All collaboration features have to work in real time (I've attended meetings via Google Doc).
So if it's cheap enough (and given that it doesn't have it's own file format, so a very small switching cost), this may become a viable alternative to Google Docs.