Have to say that now I have been using both the ipad/gns and iphone 4 (both with Air Nav Pro) for a few weeks in anger, I hardly look at the ipad now, but find the iphone (suckered to the side canopy) is sufficient. I didn't even bother taking the ipad today.(I do have a 296 also in the cockpit but don't use that either now!)
Depends what you do, I suppose, but for VFR planning & referencing it's as good as you need.