Well less of a model to predict blocks/day and more of a way to measure performance. For instance, it could help someone tweak their setup to finding longer chain lengths instead of shorter. Or really, just help people understand what their tweaks are doing to performance
Exactly. Even if the prediction is way off, that isn't a big problem as long as something half the speed is also equally off with half the prediction. Need some way to compare hardware and know which machines are faster miners than others, etc.