Contacttower - try Goodreader, much better than iBooks. Not free, though.
I've played with iCharts (EAG, private subscriptions not available yet but you can use the sample data) and the Jeppesen app - indistinguishable, really. AIP charts don't display well on the iPad, too fiddly.
I had a play with my iPad on Wednesday in the sunshine at Gloucester (that was me in the blue and white PA28 from about 1015-1115, if you were there!) and found it
a. too big to yoke mount on a PA28 - barely fits in the space!
b. too big to mount on the glareshield
c. fits nicely on my kneepad
so I think I will be looking further at EFB uses for it, and buying a proper aviation GPS (Skydemon?) to replace my Airmap 1000 now the latter doesn't get any database updates (gee thanks, Lowrance...)
Tim