Im not evolved enough to be able to detect differences in vertical compliance. Im usually hanging on for dear life or praying the landing goes as planned;-) Though, my intuitions about carbon rims correspond well with this article (warning: Math).
the tire deformation provides more than 100 TIMES the vertical compliance than that of the wheel, whether it is aluminum or carbon. It should be clear now that not only can no rider can discern the difference in vertical compliance between any two wheels, but rather these perceived differences must be coming from changes in tire volume, air pressure changes (even a few psi makes a big difference), tire casing, or even frame/fork/stem/handlebar flex. Keep in mind that wide rims increase the volume of the tire, so if you are coming from narrow aluminum rims to our wider carbon rims, not only should you not be worried about less vertical compliance, you should actually expect an increase in vertical compliance (comfort) due to higher tire volume!
Ive got more than a year on a set of hookless 35mm on I9s from Nobl. I went the safe route with the 35mm because I live at about ~190 in the winter (and Im a hack), but Id be temped to go narrower next time. The rear has an HD layup and was built with competition spokes. Trevor built up the front with CX rays, with no HD layup. I never weighed them myself, but I think they were ~1650ish.
Id have no problem moving these to my hardtail. I was coming off Flows (29) that needed frequent truing, and felt pretty loosey goosey, so I really like the continued stiffness in pretty much every situation. Moving them up hill feels money.