Kamper -
Thanks for the note!
We put up the tacky plastic window sheets this weekend. I'll keep in mind the ones you mentioned for next time, tho - I honestly hadn't heard of them!
I also didn't know about the vents you mentioned - we were just up there this weekend and decided not to insulate more right now because it's pretty thick up there. It was about 20 degrees when we were there and it was about 40 in the attic, so it seemed tight enough. We did replace a vent hose from the upstairs bathroom that wasn't insulated - that was a lovely find (NOT!) because it was way too long and full of water. Good thing we found it before it started dripping or froze.
Last night, the baby decided to get into bed with us and was all snugly under the electric blanket with me when our 6 year old came in complaining of being cold. "I want a 'lectric blanket, too!"

I scooped him under the covers with us. He wasn't cold at all (our cat sleeps at his feet even in the summer - he's all set!) but felt an injustice was being done!
Thanks again!
-AW