Danlib1,
I compared it to the Antique Sound Labs MG Head DT OTL mk III (say that fast 3 times) and the Grado RA-1. I preferred it over these two with the stock tubes. The Woo sounds even better with the Mullard tubes as well. IMHO, I don't think you can beat it for under $500.
I also used it as a preamp for a month while I was between preamps. Although it didn't embarass itself, sounding quite sweet at times, I wouldn't recommend it as such. It was a bit noisy and limited operationally for my preamp tastes. I had just sold my BAT VK-31SE, so it is quite a step down from that, as one would expect.
As for customer service, I wouldn't say they are the best either. The unit comes with no manual or power cord. If you buy direct from Woo Audio, they e-mail you a 2 page manual, which tells you there is no power cord. I haven't had any service issues, so I cannot comment on their response. It did take 3 weeks after my order to receive my unit. So overall, I wouldn't say that customer service is their fortay. They do make a good sounding head amp though.
Cheers,
John