I find it quite useful in situations where I literally can't increase my quality anymore with the CP I have. An example would be I'm at 20 durability left (If I hit 10, I can't use Manipulation...), and not enough CP for Manipulation, so I can't increase quality anymore without likely botching the synth. So, I can use Rumination and if I'm lucky I get enough CP to hit manipulation and get three more touches. If it's not enough, well, no more need for control if I can't touch anymore, so more CP to help me get my progress up enough.