I have the 35/50/75 Saturn in E mount and haven't experienced any focusing issues on the A1, and of course that's with no Desqueeze support. It does have a bit better EVF than the Panasonic cameras, but I haven't found the EVF to be a night and day difference.
I own the 35 & 50 Saturn in L mount and have had great results on the S1RII. The 35 isn't quite as well corrected as the longer lenses, so it has a bit of character, especially against the light. Still, none of the Sirui lenses can rival the results I get with my favorite anamorphic adapters, but there is something to be said for simplicity and reliability.
Also - I'm not sure if the S5II was included, but the recent update for the S1II/S1RII now provides 1.6x desqueeze.
Still attached from the 35 Saturn on S1RII.