Been using iPad 2 3G with additional GNS bluetooth GPS. Works a treat, and a very powerful tool for emails and the web, when back in the room (or tent). Still carry the ERSA onboard and maps onboard though.
Before flight I log in and use Eflite tm for W & B, and send it to myself on email for printing.
Air Nav Pro - Love it and the best planning tool I have found and very useful in the cockpit as a moving map display. Bit expensive buying the maps, but once you have them they are yours and survive during Apple upgrades. Gives clear Airspace areas, and zoom in zoom out function is easy using two finger Apple method. You can set up your own waypoints, and change between charts easily or overlay charts. Head up or North up function works well. Easy to move around Waypoints after route has been created.
I've tested and trust and use the raw data and apply it through Sportys E6B (flight computer) app. to write up my kneeboard. Easy Peasy.
NAIPS - very useful tool for weather info . Great tool for flight planning and lodgement, once the kneeboard has been written up and you are ready to go. Have used this in the room before a flight and sometimes in the cockpit before a flight to lodge plan and Sartime.
OzRunways - These guys have it nailed, but I find their newly introduced flight planning not as good as Air Nav Pro. But that may just be me! It has the electronic ERSA so Runways are available to you, but good to carry the Country strip books as well, if heading away to the bush. With easy map chooser and secondary moving map for the cockpit I can load up the ERC low and change to it from time to time to see I am on the right frequency. Nice to have the electroniuc AIP as well, and not such a need to keep up the paper version now.
Pkt Weather - Simple and easy and just add your destination to get the daily weather forecast up to 7 days. Nice window to OzRadar functionality that I have used live to skirt around showers.
Trails - Nice little App that picks up your GPS and leaves a snail trail on the map of where you have been.
Dial a Wiz - got onto this nice little number for my iPhone and have used it quite a bit, to get local weather, both in the planning and the flight stage.
I am pushing the developers of Air NAv Pro to link to ZAON XRX PCAS system. Foreflight (only good for US) has already got it and it links via Bluetooth to Garmin, Bendix/King, AvMap etc. so it will only be a matter of time before it is on the iPad app in Oz. See http://www.zaon.aero/content/blogcategory/30/47/
Coming from a commercial boating background, where GPS and moving map technoligy, linked to Radar and AIS has been used for years, it will be a great safety aid to virtually see other danger aircraft on your screen. This in my view is the next big thing for AUS flying. and it is not too expensive at all.