All that fuss over a few tiny scratches in aluminum? Most parts work just fine straight off the machine. Unless you're building a race engine, the extra time spent lapping seems like overkill for a daily driver.
Hand-lapping does give a great finish, but it's not always the best first step. For example, on softer metals, rough lapping can push grit into the surface. I saw this happen on an aluminum piece that got tiny scratches. Good cleaning before you start lapping helps prevent this. The smooth cycle is worth it, but only when you do it right.