I got a 3G iPad 2 Thursday and took it flying today for the first time. I've got Airnav Pro installed on it and it worked absolutely fine. No loss of signal whatsoever (Robin DR400) and that program is brilliant. To the point where it automatically fills in your logbook even.
I got the ICAO Netherlands map and all the database-derived airspace data (up to and including IFR intersections if you want to) is simply overlaid on that map. Works brilliantly and the feature to limit displayed airspace to anything plus or minus 1000 feet of your current altitude is genius. My copilot, an airline pilot, was seriously impressed with the capabilities.
I also have iAIP installed which lets you download all AIPs for Europe to the iPad and then browse them offline. Kind of a poor man's EFB. If I had an IR and would fly IFR I would get JeppView instead but for VFR it's good enough.
We flew some 2.5 hours today with the iPad turned on, I checked mail and filed a flightplan with it, and as I'm typing this on the same iPad it's still 60% charged.