I listened briefly and it was indeed nice. My audio vocabulary is limited so bear with me. It did not strike me as slow or soft as I have read about some Woo amps; my SR-Omega sounded good on it. It had all new production tubes, Tung-Sol 6SN7 and Shuguang (sp.) 6CA7, the newer special model. I definitely think it is head and shoulders above the A10 but that probably does not surprise many. The A10 has the Ray Samuels sound which may appeal to some but is not my cup of tea. I prefer my ES-2 to both amps but i am biased and out a shitload of money there, so go figure.
I think the Woo will be a great addition to the electrostat market. The BHSE sounds great also. We hooked up an ES-2 and the BHSE to the same source and I must say that I was surprised the ES-2 held it's own with the O2, several others felt the same but I will let them speak for themselves. But for the money the BHSE is a clear winner.