Long curious about it, I picked up a $200 20T5 recently as luckily for me it came with a barrel ding. Having long thought a Nagler set got 2nd hand makes the best and smartest high performance, mid-range cost kit and now having 31, 20, 13, 5, 3.5 and 2.5mm fl's it seemed like time to test that out from the dark site with the 16" Starmaster.
The short story is no observation made (or missed!) last night could have been much (or likely any) better made by swapping an Ethos into the focuser.
The 1st light for the 20T5 showed pure and clear E-F Trap stars before it was much dark at all. From Messier open clusters in Auriga and Gemini to reflection nebulae in Monoceros (N2245, 2247, 2261 and IC446) all the boxes were checked. NGC2158 was clear near M35 in the 20mm's FOV with good colorful stars showing well in M37 and others. Large and small irregular galaxy pair NGC2366 with its super star cluster/H-II knot and little NGC2363 floating off the end was well displayed via 13 and 5mm.
But the most fun was NGC2680/NGC2679 that appear as 2 Gx with unequally bright cores in a common halo. But N2680 is a double star and the mission was to split it. I took it up to 839x with the 2.5T6 without success and decided to pull out the 3.7 and 4.7 Ethos to test this whole concept but they too failed just as the more modest Naglers had.
I don't think they are THE BEST, #1 CHAMPION eyepieces in the world. But I think for most of us, our gear and our habits it would take some powerful argument to convince me there was an observing task we are capable of that they are not.