foldingstock
I find that by logging workouts and measuring progress, I am much more likely to improve and know by how much I improved. Logging workouts can also save time. By logging my workouts, I know exactly what my target goals are for my next workout, so I can get in and get it over with instead of wasting time doing what "feels right" at the time. This works great for me, but YMMV.
I pretty much stopped reading here. Elusive to objective metrics? I agree that you can't measure a program like you would a bridge, using physical laws such as physics and chemistry, but you very well can measure many aspects of it such as: efficiency, size, required resources, relative ease of use, etc. Just because it is not a physical thing doesn't mean we can't use a "scientific method" approach, we just need to be open to using metrics that exist in the digital realm.