Congrats, my brother in arms. '7' is a huge step in the Navy. '8' just meant I got paid more...
But to be honest, in the Marine Corps they treat their E-6's much better. Promotion to E-6 (Staff NCO) is just like Promotion to E-7 (Chief) in the Navy so things probably won't be too much different for him... except where PAY is concerned. You earned it, enjoy it!