Shorter shock length is one pro. As is having a variable rate of arm movement vs. shock travel. As the arm moves in compression it has less leverage against shock, simular to variable rate spring. Also allows for a shorter shock.
Cons: Complexity=more parts.
Fabrication: Say if you were to copy the Banshee geometry, very careful measurments would need to be taken. I would dare to guess that even 1/16" would throw it way off. X(
I have seen mention of Banshees and TRX250r going to link less, I don't know particulars though.