I've tried taulman 645 now, and it is definitely more difficult to print with than 618 for me. When printing the bracelet for example, it works fine, but with parts that have lots of retraction it is under-extruding. Maybe it sticks more to the bowden tube or something. It is more translucent compared to 618, and at higher temps it seems to "crystallise".. currently using 245 degrees, 2,5mm retraction, 3,05mm nozzle setting, 0,2mm layers.
Edit: The layer bonding seems to be better, and it's less brittle I think.