Got a brief test in tonight but it was horribly windy and lots of cloud, got about 10 minutes with the ES 20mm and about 1 minute with the Pentax zoom at Saturn before the weather deteriorated.
Hmmm. Have to reserve judgement due to the conditions. Also my only comparison is to the Bintel plossls.
First impression of the ES is that it's almost too much eyepiece, not sure if there is a technical explanation but my pupil felt like a goose being prepared for foie gras!

This is not entirely a good thing, but it may take some adjustment, had to move my head around to scan the entire view, maybe I'll get used to it.
That said, the Orion nebula was nice, I wanted to do a side by side with my old 26mm but those damn clouds foiled me.
There certainly was more of it at 20mm then what I've been able to see in the 26mm and it was crisper, but I think I'm being robbed by suburban light pollution.
A brief break in the clouds brought out Saturn, so I quickly switched to the Pentax, lined her up, and fought with drifting clouds. Sliding the zoom up put a smile on my face, had to adjust focus slightly as I moved up and at 6.5 the seeing was to poor but I have the feeling this one is going to get a lot of use.
Contrast seemed good but it was the briefest of first impressions and Saturn was low on the horizon so I'm looking forward to what this can do.
Will update again when the weather improves...