Late to the thread, but had to add, as I dive Winni quite often.
First of all, Tom @ Dive Winnipesaukee is a great local resource. This is one of the few dive shops anywhere that has a fully-equipped dive boat docked right out back. They run charters on Friday evenings (cheap, rental gear included...one-tank dive), and Sunday (rental equipment extra, two-tank dive). They usually hit the more popular dive sites on the Lake, but also take requests. Policy is that if anyone requests the Lady of the Lake, they dive there first (it's pretty much furthest away). But they also like to hit Welch Island, the old Navy testing site off of Diamond Island, Rum Point, the speedboat wrecks near Ship & Moose Islands, the wall by Parker Island, and other spots. The crew is most helpful. Can't say enough about this operation.
As far as tech dives in the Lake...I'd say not really. The best diving is between 20 and 40 feet...at 80 feet, you're essentially in the dark. The Lake does go quite deep, but you're not gonna see anything.
There are also multiple uncharted wrecks around the Lake. 70 square miles of glacial lake means a lot of diving diversity.