One of my friends has one from the 70's and he swears it's the best thing since sliced bread.
He gets into it nice and toasty and hangs about a bit before bed, slips his boots off, pulls the elastic ankle cuff bits down so his feet are covered, puts the hood up, and then he goes either under a tarp or into a bivvi bag for the night.
If he does need to get up he's still warm and it's easy to go back to sleep.
In the morning he just gets up and footers around making breakfast before he gets himself dressed for the day.
His is cotton covered though so safer near fire.
I don't fancy those dayglo coloured ones much
cheers,
Toddy