I have the Burson Headphone amp, and I really like it.It's not got 50 hours on it yet, but no strange noises and my room has flourescent lighting (pot lights).
I use an aftermarket power cord, and prefer the sound this way, but I don't feel I can really comment until I put some more hours on it.
Also because this unit is so good, I plan to upgrade my cans,so that will be another time consuming variable.