It's great. The ZX2 is maybe the best dap for sensitive IEMs. So rather than getting a DAP that is a compromise on SQ by spreading itself too thin trying to please everyone, the ZX2 is great at one thing.
I wish sony would have made two version like this: one clunky high powered one for people who want to use hard to drive headphones portably (why?) and one small svelte lower powered version for people who use IEMs.