Omnifocus is the only thing I found when I switched to the Mac and OL2011. I used to have PC with the add in and it was great. That said, OF does make me "focus" more on managing task and projects where GTD for Outlook is integrated (good) but a little cumbersome inside outlook. OF does make you double entry but maybe there is a 3rd party software that would link the two.
i just started so I used the free 15 day trail from OF.