As Firefox is heading towards mobile space it’s pretty obvious that the user interface, which is designed for mouse driven computer screens really can’t handle today’s touch-screens and whatnots.
The initial impression is that this really looks nice as far as user interfaces go. However, if you want to go heuristic on this, in the light of usability, the lack of visual clues in the default view might become a problem. However, if proper tutorial/tips are provided this shouldn’t become a problem.
Also I’m not sure if, in the end, I like the drag controls. Sure, it’s nice with such small pages but what if the user navigates to a page which is far wider than the mobile screen can handle? After all, such pages are hardly uncommon in the internet.
Not to mention the user interface has two completely different operations in the same direction drag (drag to right/reveal left – either browser controls or back to all tabs view), only the length of the drag defines what happens. However, with proper execution and clues I think this could be handled;
50% screen (or less) drag/reveal = browser controls
90% screen drag/reveal = back to all tabs view
This way user could rely on muscle memory when using the interface, thus using it faster and more reliable, instead of conclusions based solely on visually observations.
Video after the jump.
Read: Aza Raskin’s blog or Mozilla Labs blog