JavaScript vs Java (GWT) components

Vaadin 7 brought us redesigned and greatly simplified component development approach. Developing client-side JavaScript-only components is really simple now and JavaScript support seems to be complete to enable development of complicated components.
Though it is stated "
It’s really up to you
" I’d like to know if Vaadin core developers would recommend using this new approach with (or instead of :bashful:) traditional GWT way or if JavaScript components are supposed to be used only for prototyping and applying quick hacks. And of course it would be nice to hear about any real-world experience from other Vaadin users.
So far the only severe issue I have is