I'm using outlook 2011 for mac.
I like it. It is not as powerfull as the windows version.
I'm using tasks and flagged mails to populate my list.
(the only thing to install are a couple of folders, some categories, and some rules)
for example when I have a mail that needs to be done and I have to surf the net for something as a next action.
I forward the mail to myself (I have me as a contact)If I have to reply after the search I forward it as an attachment.
I change the subjectline to maco: find ... and hit cmd+ enter.
a rule recognizes a mail from me to me with the 'maco:' keyword and marks it as read, flags it (no due date), adds category maconline and moves it to a folder.
In the task view
I have my different categories. When I select Maco: I'm looking at all the next actions for this week where I need to be online.
I have an app 'captio' on ipad and iphone which only send an email to myself. There I'm using the same keywords.
The basic 'engine' was made by a friend of mine who works for MSFT.