Very strong case for Porter's general verbal aspect system. Helps answer the question of how temporal relationships are encoded in Greek if not in the verbal form.
I find it helpful to skim the historical and practical explanations of verbal aspect in each work in this series (even though there is a decent amount of content overlap between these sections and Porter's book, PVA). It helps to keep my mind working from an aspectual standpoint as opposed to temporal when reading the Greek NT.