Time and again I have been struck by just how unsporadic Es is. OK, good days are random but there seems to be a pattern that more northerly and Scandinavian stations on 10m and 6m are better later in the day and later in the season. I actually wonder if these more northerly reports really are Es at all. There is every chance I am totally wrong, but I have noticed this over several summers and I question that Es is truly "sporadic". I'd be interested to hear the views of others on this.
One thing is certain: we still have a great deal to learn about E-layer DX propagation. Es is certainly a fact on many summertime EU QSOs on the higher HF bands and 6m, but I am sure the multi-hop explanation for some very long distance QSOs is not right.