I've now had an opportunity to test out the iPad/ForeFlight combo on a couple of 7 hour flights involving some relatively high workload flying (IMC, night, etc.) and must say I am very pleased. I used it as my exclusive source of VFR charts, IFR low level charts, and approach plates, and also ended up using it for airport info as the information is just so much easier to access than through my Garmins. I had a couple of minor problems with ForeFlight crashing, but because the app comes right back up at the press of a button, it was not really an issue. Battery life is superb, and the iPad screen was readable in all light conditions including at night.
The only significant shortcoming I uncovered was this: The low level IFR map may occasionally lack certain info where the source maps have been stitched together. The specific problem I experienced was that my clearance included an airway that had a bend in the middle defined by an intersection. On ForeFlight, I could only see the first four letters of the intersection name; the fifth letter had been lost by whatever process is employed in stitching the source maps together. Thankfully, it was the last letter and not the first, which allowed me to input the first four letters into my Garmin and then scroll through the options, checking lat/lon coordinates and discerning which of the available intersections was the correct one. So, for now, I will keep my good old paper charts available for backup.
M