There's one seam on the ceiling that has a pretty drastic height difference between panels (3/8" - 1/2" probably), which is a direct effect of not having had a nailing surface along that edge (kicking self). Maybe I'm being naive, but I think we can take care of it. Smeared a whole bunch of compound along that area and already it's looking better. Tonight we'll sand it a bit and then tape it per usual and go from there.
Also tonight we're heading to a local window and glass shop to design our attic and bathroom windows! After that, we plan to sand down all our work from last night. Will post back with the results!
and here's the problem spot that I mentioned: