Trying the Voigtlander 17.5mm
I know this is not answering your query.... I was fascinated by the CV 17.5/0.95 and tried it out recently for a few minutes. Nice feel, heavy and slightly unbalanced on the OMD but a joy to use. But if you've never tried a MF only lens plus spend so much, I don't think renting it for a weekend is going to be enough and the "cost" of the mistake (if it turns out that way) might be too high (depreciation and hassle of selling). I'd buy a fast old legacy lens (with adapter) and practise MF and see if you enjoy/like it. I'm saying this because I did not have any MF experience, then tried legacy lenses -- difficult at first but kept at it. Then I got the CV 25/0.95 and left it on the shelf for some time cos trying to shoot at 0.95 up to 1.4 was very difficult for me. Then I tried again after a while and now I'm loving the lens. But on the whole I think the Oly 17/1.8 is the way to go cos it's got a "real" MF like the 12/2, cheaper, light, has AF option and IMHO the 17 focal length (or 34/35 equivalent) doesn't give you that much OOF/bokeh rendering as compared with the 25 (50mm).