Tilmook,
Hada ka hor ayaa nin xoola dhaqato ah keenay xoolihiisi Zeylada Hargeysa si looga iibsado. Markaa halka uu ka filayey in lasiiyo lacag tiro bad oo Shilling Soomaali ah ayaa waxaa la siiyey in laba jeer ka yar intuu filayey oo Somaliland Shillings ah. Kolkaa wuu yaabay. Markii uu ku laabtay rerkiisii ayaa wuxu ku yidhi xoolihii wax badan la igama siin sababtoo ah 'markaa aan koob shaaha cabo, Ina Cigaalna mid ayuu cabi".
It means the SL shilling is worth twice as much as the old Somali shilling. It's double the value and essentially stronger against the dollar. Downside is it's only accepted in SL. The upside, it's not as compromised as the old Shilling Soomali which has been subject to money laundering.
As for being interchangeable, in Erigavo they are. That is why Somaliland is attempting to get rid of, and make SL shiling sole currency there like they did in burco.