I'm currently running it on the iPad 3.
I used the iRig connector at first but it was noisy, then i tried the Peavey Ampkit link which is better.. Now i use the Istudio which is a mobile dock and allows the Guitar plus another input and mixers..
As for the App
Good range of models of Amps, Affects, pedals and can be used with the Griffin 30pin foot controller or the a Bluetooth pedal like Airturn...
You can run the App in the background and use another app at the same time..
Great App, Amazing sounds.... I recorded a Demo and my drummer ask if i'd bought new gear cause it sounded like a Tube stack... i laughed and said it was a App... As for using it live.. I couldn't help but take my pedals and Amp but I'm sure you could plug this straight into the P.A... I suggest taking a Cardboard cutout of a Marshall stack just for Show