I have a BP2 dx and go with little to no sleep when hypo. That is between 0 and 2hrs... and yes I wake up completely well rested. Sometimes I plug in my headphones and dance while I clean my room or do a load of washing while I wait for sunrise.

That being said, I naturally get by on little sleep (average on 4hrs) unless I'm depressed.
It varies from person to person, but sleep disturbance is common across the bipolar spectrum.