I just finished a longish evening of RA4 printing at home, and spent my time with Ektar 100 in 120. I've been printing 11x14, so I can't really scan my prints, but I thought I would pass along a few comments:
* Ektar 100 is an awesome film. It's so fine-grained that it's nearly impossible to properly focus on the dye clouds using a grain magnifier. It makes me want to print bigger and bigger, until the grain starts to appear. The saturation is also pretty much at the limit of Supra Endura's ability to render rich colours like red.
* Compared to a scan, an RA4 print is a little bit softer, obviously because there is no artificial sharpening, but perhaps also because of the finesse of the grain (cf. Thornton' oft-quoted correlation between grain and sharpness).
* If you only had scan-and-print prints from Ektar 100, you're missing something very tasty. I've always found RA4 prints from scans to be plasticky and without substance.
* Filter pack was rather consistent between photos taken in comparable light, but every once in a while a photo revealed a subtle cyan or red shift. It's definitely a film for the blazing light of noon.
* Shadows are very blue, something that is not always apparent on a scan.
* I suppose the dyes of Ektar 100 are more modern than the dye chemistry of Kodak Supra Endura. Perhaps this would help account for certain discrepancy in hues: yellows are much less pure on RA4 than on a neg scan. Has anyone tried printing Ektar on Fuji Crystal Archive?
* All that said, it's definitely a film well positioned for a hybrid workflow, since it scans so well, but properly printed on analog RA4, it will yield not just saturation and detail: it will also yield that Aha! moment.
* My Mamiya 55mm f/4.5 (TLR mount) is a gorgeous lens.