Well, to report . . . Water temperatures ranged from 77 to 81. Peter dove his 5 mil suit with a 2 mil hooded vest, and I dove dry on all the dives but one.
I absolutely LOVED diving dry, and would do it again. (In fact, after my experience on this trip, I may never dive in a wetsuit again.) The one time I dove wet, I didn't feel the least bit cold during the dive, but once I surfaced into the wind, I started to shiver, and it took quite a while to get warm. In the drysuit, I'd get out of the water just as comfortable as I went in (despite some leaking issues here and there).
I used my Fusion with a set of Lands End Polarfleece sweats under it. I wasn't overheated getting ready, and I was deliciously comfortable during and after the dive. And I did my tech dives inflating on backgas (with 21/35) and didn't get cold.
Peter was generally comfortable, but we hit some thermoclines (one of 7 degrees!) where he got pretty chilly. He says he'd probably dive wet again under the same conditions.