Do you mean in terms of the editing interface, or the content that's produced? Editing on mobile devices is something to address in the (far distant :) future but we want to get it right on modern browsers first. If you put your email in at the end of the initial tour you get a more detailed demo that only works in Firefox, but shows you in a lot more detail how it all works. Our goal at the moment is to build support to launch a crowdfunding campaign to finish it off ... although we could theoretically finish it off with our own funding, we don't want to keep toiling away in obscurity so getting "backers" is basically like getting "validation" right now.

The goal would be: release just the basic functionality we have now with key improvements to deployment and obviously making it work in all modern browsers, then iterate from there according to customer demand with features (including things like editing from tablets and mobile devices) being prioritised by engaging with our user base.

Basically we've just spent too long working on this with absolutely no engagement with our target market (designers/devs) so we want to get it out in the open and see if it's actually worth finishing.

EDIT: If what you're referring to is the content being produced, then the fact that the markup and editing experience is so highly structured and the fact that the user is unable to put any presentation logic (fonts/sizes/styles etc.) arbitrarily in with the content unless you, as the designer, have explicitly allowed them to do it, the format is so reliable that repurposing the content to different devices is very safe and reliable -- ie. it doesn't really matter that the content editor can't preview on multiple devices, because you know that whatever they enter in, the format will be so predictable you can make it look good on any device.