There is sort/group by already; check under 'options' (bottom left of the box on the right of the gmail window), although I would like the ability to sort/group by more things, such as which list things are on (not just limit it to the view of one).

For a clean GTD implementation, group by, sort by, and filter by are all needed for @contexts (which seems to be what the "Lists" feature is for), and for projects (which seems to be what "tags" are for).

I'm amazed at how often this primary functionality is just not present in task management tools. Apparently RTM can be hacked to do GTD, but you shouldn't have to resort to hacks to get this kind of fundamental functionality.

Don't see sort by group in GTD, am I missing something?