I've had my iRig Nano for a few days now and this is just an initial impression of the item. The size was a little larger than I had expected, but it can still fit inside my guitar case, which is a plus. Exterior construction seems to be rather light duty. Cheap plastic, with some questionable choices for switches. The kick stand looks to be pretty delicate. Time will tell how well it holds up. It is also 100% battery operated. No option to plug it in, so I'm curious what battery life will be.
Playing through the built in speaker: There is a gain knob, volume knob, and a bright switch. The tone is okay for a small portable speaker. The 3" speaker allows it to get loud enough for practice at home. You can hook it up to an external cabinet and it does a pretty good job powering it. Not loud enough for a full band, but would totally work for jamming with a friend.
Playing through the headphones: You must use the AmpliTube software, which is a bit of a bummer. From what I can tell, you cannot plug in headphones and jam without plugging in your phone and launching the app. The app includes features like a tuner, metronome, drum track and multi-track recording, which is nice. There is a pretty big learning curve with the software, and I haven't been able to figure it out completely. You will also be constantly prompted to buy more plug ins, which is probably what justifies the low price of the amp. You basically have one amp modeling option, one cab option, and one or two pedal options included with the software. All other plug ins will cost you, and they are expensive. The sound is pretty good with what I've messed with in the app though, and I would imagine the add on features only sound better.
For the price, it's a good option for those looking for something portable with the added bonus of hooking it up to your phone. You can put it in your case and will always have an amp to play through. If you already have invested in AmpliTube software plug ins for a different interface, this thing seems like a for sure win.