I used Google Notebook for a while, but I thought they shut it down years ago, not long after I escaped with my notes to Evernote.
I would love to use a simple editor which syncs to my Dropbox text files. I've seen some apps which do that but they try too hard to be cool and go overboard with their javascript animations, making them unusably slow. I might write my own.
It's a shame it's hosted on Google App Engine though. Given their new pricing changes, you might have to move it. Maybe you should launch Noogle Gap Engine...