You know an OS is great when it it makes MS Outlook even slightly tolerable. In this case iOS 5 adds syncing Exchange tasks with the new Reminders app in iOS 5. I have avoided uses Outlook task since my first iPhone arrived. I preferred to hop from my work windows machine to my iPhone or iPad rather than use Outlook any more than I was forced to.
I missed it in many of the great iOS reviews but discovered it last night when my old completed tasks from work showed up in Reminders (>4 year old tasks that were surprisingly completed).
You can find more here at the Macworld iOS 5 FAQ.