Basically, one of the "big deals" is the ability to drive long interconnects with a high input resistance at the other end with minimal voltage (gain) loss. Also, the xmfr acts like a filter which does not amplify the tag-along garbage that the signal carries. As always, there are no free lunches, but a well-designed xmfr coupled output stage can have advantages over a cathode follower output - but the xfmr has intrinsic and application imperfections that have to be considered (such as it has to be sized for the average DC current and the harmonic distortions introduced). Not better, not worse - just another audio compromise
What does "transformer coupled" mean?
I've read about preamp designs that are transformer coupled (Audio Note, Supratek, others?). What's the big deal about transformer coupling?