I played a few games I really enjoyed, but I either finished them quickly or didn't replay them enough to justify the subscription. I was also a little burned by two of the story driven games I played (Jenny LeClue and Guildlings) being incomplete - story just ends with vague promises of more to come. There are some fantastic games on there - What The Golf, Assemble With Care and Over The Alps are all great, but having completed them and seeing how few games were being released each week to move onto I just didn't see why I was spending the money.
I'd rather see them add a curated list of already released paid apps to the service a-la Playstation Plus when new releases are thin on the ground than see nothing come out at all. Or they should bundle this in with their Apple Music subscription. As it stands it was great value when it first came out, but the longer it goes on with very infrequent additions then that perceived value is just going to drop and drop as you finish or get tired of existing games.