to me, the colab aspect of this is only interesting in that all stake holders have access to the original work....it's a pain when you're working in photoshop and have to deal with a) marketing folks that don't know how to use it, and b) developers who don't use it at all.... would be pretty excellent to be able to do all your design work in a tool like this, and have it shared equally with everyone, so the marketing team could have their input (ie branding etc) and the dev team can see it for accurate measurements and elements etc.... I'd be down with using this....big time....

edit.

just sent the link to our Product Manager and lead developer... waiting to see what their interest is... as for me, I'm thinking this looks great :)