Can't help you Grahame but I had a similar experience when Sigma brought out their "Merrill" series while I was still on Windoze XP.
I bought a DP2 Merrill camera and dutifully downloaded the required latest converter. Moving a slider caused up to a minute wait as their bloody converter redid every slider setting from scratch! (that's what it's always done, unlike other converters). OK for the previous model with it's 12MP raws but 40-50MP, ... fuhgeddaboudit.
It was so bad that I sold the camera within a fortnight ...
P.S. by Sigma standards, 2 to 5 secs is positively streakin' ...