I use both PlanPlus 2.0 and the GTD Outlook Add-In. I find quite a number of benefits from using both together but fundamentally they let me look at tasks and work through different lenses, and I find that useful. For example, the GTD add-in lets me view tasks organized by actions or organized by projects. PlanPlus makes it easier to sift out only those things that I want to focus on this week or today. I think of it as taking getting things done to getting the "right" things done.