I can't say I am surprised. Most other airlines (European and American) have gone down this road and since the financial performance of SAS is far from stellar yet they need to get more revenue streams. The credit card fee attempt failed to even get of the ground. However with the size of the long haul fleet, this is not going to generate massive amounts of profit.
If aisle and Windows seats are preferred, that would make 6 out of 8 seats in a row preferred in the first Go cabin. Adding in the bulkhead and emergency exit rows in the second Go cabin, the number of free seats have gone down quite a bit.