I honestly consider this to be the highest technical quality film stock available on the market today, all things considered (sharpness, grain, colour fidelity, etc.)
Medium-format slides on a light table have a jewel-like quality unparallelled by any colour negative film or scan.
E100 in particular has a slightly lower contrast and wider dynamic range than other slide film stocks (most of which are now sadly out of production anyway...), which makes it more of an all-rounder - provided that one knows how to expose properly.
The colour balance tilts towards the cool side (in other words, it looks as if it was calibrated to something like 5000K instead of 5500K), but this is easily compensated by using a warm "light balancing" filter like a Tiffen 812 or a B+W KR3 - I use one often with this film, except in direct sunlight (where it isn't needed).

I enjoy shooting this film in the winter, finding that it works well with cooler tones. The few rolls I shot in summer came out with skies blown out and very dark shadows.
I haven't had a bad exposure with the Pentax 67, this film seems to expose differently on 35mm, it's much better to work with in 120.

It just is. It doesn't have the saturated colour that Kodachrome did, but then Kodachrome never came in 120 rolls. I have pictures from '87 taken on this film, 35mm. It lasts over time and it's colours, on the cooler scale , are true. Ar it's best under wi ter syndrome, you can try and push it to it's limits regarding available light. And there is one other thing. It's exposure latitude is crucial, it won't forgive poor technique! Note: All pictures are archive 35mm Ektachromes from 1987 taken with an inexpensive Practika PM3 SLR camera scanned with a plustek 35mm scanner. Archive quality. Currently using a 6x6 Seagull twin lens reflex with a phone app light meter. 😀
Cheers, Duncan.

I know, being the best is subjective, and based on criteria we all have different needs for. But I think if you were asked to take one camera, one film, to capture something amazing and one-off that was going to happen; you better take this. Unless that one-off thing was a contrasty sunny day with harsh side light, then better off using colour negative. I save this for special occasions.

I had long feared shooting colour positive film for its reputation of being unforgiving, but I'm really happy with the results with Ektachrome. The colours are vibrant and punchy thanks to the built in contrast, and I didn't find the metering too bad at all. Definitely something I'll be shooting a lot more of