I have an iRig also, a b-day gift from a friend. It's a great pocket/practice amp. I tried using it as a sorta preamp/DI into my PreSonus....but that didn't work so well. That's not what it's meant for anyway, so I'm not complaining.
Actually, you'll see comments from IK where they do specifically talk about recording, using it live, etc. I honestly don't know how people are doing that as I think it sounds horrible.
I think a lot of the quality could be due to the iRig. They have an antifeedback feature in the software specifically to keep the iRig from feeding back, at least that's how I understand it. If I try to run the free AmpKit I get horrible feedback unless the volume is set so low you can barely hear the instrument.
I guess that's my running complaint. The volume output is simply so low you have to jack the gain/volume in the software so high it then sounds horrible. I don't pretend to have the technical knowledge to know WHY, I just know both myself and my wife thinks it sounds HORRIBLE.
Normally troubleshooting is a process of elimination. I have tried two different apps now, and both an iPhone 3G and current iPod Touch, they all sound bad when using the iRig I have. I wish I had a different iRig to try, or a different interface all together.
At this point I feel like i'm BETA testing this stuff, yet paying retail for it at the same time. It's left a sour taste.