It works great with the DC filament upgrade on power hungry headphones like the AKG K-1000. It would be a poor choice for highly sensitive headphones that only need a few tens of milliwatts of power though.
PB is alluding to the fact that I used 300B amps (Paramounts rather than a Kaiju - Kaiju with DC fil upgrade is even more quiet) to power one of my pairs of K1000s before we made the Neothoriator for them.
You can see Peter Breuninger listening to this setup at RMAF several years ago -