I've got one of the schnozzle bags with a compatible mat. It is categorically not cumbersome, not tedious, weighs the same and is filled with down so it has an R-value[1] of 5.9 instead of 1 which is what really matters when you're using a sleeping mat in a tent on a cold night.

[1] The R-value is a measure of how insulating a mat is, higher is better.