The Audio Note, EAR (E11??), the big Jadis and Atma-Sphere (P-2) preamps are the only high-end audio transformer-coupled units out there to my knowledge.
Transformer-coupling is common in professional tube gear, particularly from the 50s and 60s. This is because the equipment had to match to the 600 ohm balanced line standard (which is still very much around today). Tubes coupled by output coupling capacitors would never be able to play any bass driving a 600 ohm load!
We built the P-2 (discontinued when it was replaced by the MP-3) so it could drive the 600 ohm standard as well. The nice thing about the 600 ohm standard is that it ameleorates the role that interconnect cables play in the sound of the system, which is why the standard has been used for the last 5 decades by the professional recording and broadcast arts. Its always been a puzzle to my why audiophiles are so slow to embrace the same standards, despite having the same concern about cable qualities. This has spawned the high-end audio multi-million dollar/year cable industry.
We're an OTL manufacturer, but we've been a major supporter of balanced line technology for the last 14 years (mostly due to prolonged exposure to the recording studio); our preamps support the standard using direct-coupled ouptuts, which is the only other way to do it as capacitors won't work (since no-one would take a tube preamp with an electrolytic output coupling cap seriously...). IMO, its a shame that more manufacturer's aren't wise to what's happening here (sorry for the hype blast).
