I thought my edges were not too bad and was planning to do a little stone work on them.
Then I got my new skis, felt their edges, and said "Oh wait... now I remember what sharp feels like."
So I did the full tune on my old skis (coarse stone on edge hits, medium file, fine file, coarse stone, medium stone, fine stone). Even had to take the sidewall down a little more in one spot. Finally got them sharp (though still not quite as good as the machine tune on the new ones).
Of course, I skied on the new skis and the old ones sat in the car all day.