Bill and Christian have started sheet rocking the upstairs bathrooms and ceilings with 4' X 8' or 10' sheet rock from Home Depot. The ten foot long pieces are great for ceilings of fewer joints and the above bedroom took just two boards. We have decided to use a 3 5/8" pre-primed pine cove molding where the new ceilings meet the old plaster walls. This will cost about $200 and look lovely.
The smaller sheets have more complicated cut-outs for bathroom fixtures etc.and fit the spaces best while being easier to handle.