How does it sound really? Together with my Sennheiser HD545 Reference it sounds splendid to be short. Since I wrote this I have listened more. My impression is that the amp leave no traces behind, sort of speaking. I find that the colouration of the sound is minimal, none in fact.
I have tested with LT1115, OPA627 and OPA134. All of them are very good, can't hear any difference but I'm sure other people can. Drop me a note if you have any interesting information in this area.