Neat, simple. Depending on the language selected from the menu, colours and antialiasing may make the text a little difficult to read. Not as many features as Etherpad.
When I look at collaboration tools for writing and editing, I break them down into points on two axes of time and space
A blog is a reverse chronological accounting that uses space (scrolling in one dimension) to indicate the passage of time. A wiki is a fixed space that changes over time, but includes history
An IM session is live, with no editing, allowing synchronous communication with viewable history
EtherPad and SubEthaEdit's collaborative writing allows synchronous editing
virtual space (the medium of the document)
real space (many people simultaneously writing in different places)
Zoho Writer is appealing. I have never tried concurrent edits with multiple users … I might take the Zoho expression "Lock your documents while in shared mode" to mean that whilst multiple users may access a document, no more than one at a time may edit (not true concurrency).
Zoho Forums, a primary means of support, is exceptionally difficult to use, a great disappoinment compared to some other aspects of Zoho. However, to their credit: the writers there are both responsive and pollite.
AbiWord 2.6.4 for Windows runs with Darwine (without Microsoft Windows) on Mac OS X, but default Times New Roman font seems to be mispresented as Dingbats.
There's a workaround or fix for this, AFAIR the symptom ceased after I used TRiX (bundled with the kronenberg.org build 1.1.5 of Darwine) to install its three suggested categories of fonts.