Don't expect the best quality from this preamp but it is definitely worth the money. The grounding in the power supply isn't the greatest so you'll get a lot of electrical noise coming through if you have this near several other power cables but easy enough to navigate around if you just move it a bit.
Other than that, this thing can push headphones stupidly loud, and the quality remains perfect until about 80% or more and then you get audible distortion, but at that level you're definitely damaging your ears anyway!
For reference, I use the amp with both Beyer DT770 Pro's (80 Ohms) and Audio Technica M50x's.