Eliminates the need for chief LEO signature and finger prints, but other than that, it allows for you to have your family members (or friends I guess) on the Trust and thus the ability to possess the Class 2/3 item legally without you being there (and when I die, I can pass my class 2/3 stuff on to my kids without the hassle of a transfer fee as they are already on my trust).
NFA items owned by individuals do NOT incure a transfer fee when you die. They transfer to your lawful heir on a tax-free Form 5. For more info on this see: http://www.atf.gov/press/releases/1999/09/090599-openletter-nfa-estate-transfers.html