Yes, they are worth it.
I book CYs when it is the least expensive option for a 1-night airport stay or for 1-night stays when I do my annual drive to/from my second home as I often have a choice of FFI and CY and am usually on the road before the FFI is serving breakfast. Also, CY usually has better beds and larger rooms than FFI.
Stockholm CY is very nice and includes breakfast for plats.