You're not the guinea pig, don't worry. That would be me. I've been listening to the PHA-2A and the Z1R for several days now... Fantastic little DAC/amp.
Construction is excellent, it's very cleanly designed, and very solid. It looks and feels more expensive than the $1000 PHA-3.
Sound sig is a lot like the ZX2 (which is a sig I love) but there's obviously more juice on tap. A very rich, textured sound, with a good amount of space and openness. Balanced mode adds seperation and detail to the bass, and brings the vocals slightly more forward. The highs remain liquid and resolving. The Z1R is surprisingly slightly more detailed than an HD800 balanced, but it never becomes rude or harsh. (Although I haven't heard the 800 balanced). Long story short, the PHA-2A is a fantastic pairing with the Z1R... In balanced mode, the two are made for each other. Perhaps literally... I wouldn't be surprised if the PHA-2A played a prominent role in the tuning of this can. I'm loving this combination. I think you'll be very happy.
Using it with an iPad Pro, and I have yet to drain the battery, but then again I rarely listen for 5 hours straight.