Hey all, I just saw that GK has their own amp app now! There is a free lite version, as well as the full version for $4.99. I do not have the instrument adapter to see how it sounds.
I just downloaded the app last night. It's pretty accurate sound wise to the GK sound. I have the iRig interface. The app sounds just like my 700RB-II used to when I owned it. Nice touch with the boost and it sounds fairly accurate to the GK sound.
There is a lot of hiss using the app so I'm not sure they tweaked it to the same extent the Amplitube and Ampkit have but overall it's really pretty good. It also includes full access to your ipod library so you can play along to all your tracks without the need to import them into the app itself. That is pretty cool but it's also limited when compared to Amplitube which lets you use a speedtrainer and looping points.
The paid version adds the EQ section. There might be other add-ons for the paid version but I'm not sure.
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Carvin LB70 4 string - All Koa Body/Neck
Carvin BX1200 Acme Low B4
A Tuner
iRig/Amplitube 2 iPhone app for practicing/recording
Gallien-Krueger Iphone/Ipad app 
