I've never shot with the pre-asph Lux, but I've had the Nokton since 2008 or so. using it on the Zeiss Ikon, Leica M7, Leica M9 for a good many years, the Ricoh GXR-M, the Panasonic GM1, and the full frame Panasonic S5. I've only stopped using it after acquiring the magnificent Distagon 35.
Yes, there is some barrel distortion which is apparent with vertical lines. There's also a characteristic circular flare, which some like and some don't. There are a few photographers on Instagram who make that circular flare a feature. The lens is glowy wide open, but not soft - there is still detail inside the glow when viewed at 100%. If I want character in a fast 35, that's the lens I go for. The f1.2 Nokton also has great character, but is super glowy wide open and much larger. The f1.4 is a wonderful walkaround lens due to its small size and weight.