I would really love to see a "QuickAdd" feature in the left navigation bar just like google calendar has. There, a one-line box shows up within the page itself (no pop-up!) and you can add something in one line in a few words without having to use a form.
In toodledo, the clever parser logic is already available for incoming e-mail, all the syntax and shortcuts for quick adds and advanced adds have already been thought of, see http://www.toodledo.com/info/help_email.php
e.g. just type "Finish the Report !! #next friday *ProjectA @work"
with !! being priority and @ being context * being folder and # being the time (all optional!!!).
I just would rather use the Toodledo web page (or a clever browser plugin) than to start up my e-mail app...