Thank god the IV is getting the credit it so richly deserves!
I love my Mark II, and my Mark I is a total badass - it never gets old to plug into that vintage gear and what you hear coming out of your amp is the same as Zappa, Steely Dan, Santana etc... they've got bags of personality and play just as good today as they did when they were made...both before I was born, in actual fact! But it's the IV which I go back to time and time and time again.
Absolute perfection as a 'desert island amp', superb.