It sounds great. It works well for most applications I imagine.
My use involved live looping into the computer and taking the output from my audio interface into the iRig.
Sadly I had to have my DAW buffer rate set higher than I would have liked to avoid cracks and pops from the iRig which ruined recordings. Whether that's due to the buffer rate of the iRig (unstated by manufacturer) or the quality of my phone (average quality Android), I don't know but its worth noting. That made it rather unusable for me, but I understand most people don't need such a low buffer rate for their projects.
The iRig app is awful with Android and basically doesn't work at all. Crashes immediately. Works better with iOS I imagine.
Overall, sounds fantastic but if you need a super low buffer rate, perhaps not ideal, but worth trying with a super high quality phone if that's what you require . If you're comfortable with 256 bits buffer rate, s'all good.