I've been to http://projectfeather.sitefinity.com/ and https://github.com/Sitefinity/feather . Other than its a "Modern, intuituve, convention based, mobile-first UI for Telerik Sitefinity" I can't find any description of Project Feather. I consider Sitefinity by itself to fit that same description, so what makes Project Feather different?
The description is on that page...
MVC Stock Widgets
ASP.NET MVC implementation of all the Sitefinity stock widgets. Take full control over your markup.
(We have ZERO MVC widgets now...feather will re-do all existing as MVC versions making SF MVC actually a practical option)
Front-End of Your Choice
Bootstrap, Gumby and bare-bones frameworks out-of-the-box. All others—supported.
(New set of layout controls who already contain the classes to the frameworks so you don't need to do anything on your end to get bootstrap..or others working)
All widgets built with a mobile-first mindset, meaning they will be responsive by design.
(Widgets are now built from scratch here in 2014...no old legacy code)
New Designers Framework
AngularJS SPA implementation of Widget
Designers. Create new designers or modify existing ones in matter of
(Use AngularJS to create your widget designers)
Widgets, designers, templates and views: all
wired-up based on a simple convention. No more mappings, no more XML.
(Same as above, simplification)
Package More Than Themes
Themes are not enough. Now you can package
your CSS, images, widget templates, layout templates and a master
template, all in one package.
(Want to sell a theme, template, and a set of widgets ...possible now)
Basically it's what Sitefinity MVC should have been...now being fully realized....but moreover YOU CAN CONTRIBUTE and fix bugs