Very nice looking, potentially useful.

I take it 'lock' is to avoid conflicts? Good idea, but do I have to activate it manually every time I think someone else might open the doc at the same time as me? Perhaps it should lock automatically if I am editing it.

Otherwise, very nice.

edit: I just noticed on your haloweb site that you made invoice bubble as well - I bookmarked that a while back when I was collecting good-looking sites. You do good design!

edit 2: Invoice bubble appears to have been redesigned since I last checked. Still looks pretty good though (I preferred the minimalism of the old one, but I expect this one is more functional)