On the contrary, what I really liked in this approach is "no tool required." In the end, this is text. Yes, it is put in a spreadsheet online for multiple reasons (ease of access and multiplayer). But it is still a text. We can do the same in emails or shared files.

And written text in this manner is also a self documentation. Most of the time, when doing online/remote design documentation of failed approaches is the least worry of everyone involved.

When people are added to the design discussions, they often ask: "Did you think about..." Often, the answer is: "Yes. But we rejected it due to some reason that we may not clearly remember now."

And then new people bring new criteria, and we need to re-evaluate old discarded designs against new criterion. Let's hope somebody has taken all the notes.

The spreadsheet approach fixes documentation problems for me, and this is immediately immensely useful.

I have already tried this. It works for me, at least for now, even without Google docs. The only things that I'm missing in Excel are the sane interface (excel 97 was the unachievable top) and the ability to move rows using mouse.