OmniPlan and OmniFocus are overly complicated. We use Basecamp to organize tasks, todos and deadlines and it is as easy as PI and pretty effective, although quite basic. I'd suggest that you take a look at it. http://www.basecamphq.com/

Another very similar service is http://huddle.net

Both are project management services, but I reckon would be very effective if applied for scheduling daily tasks.