I like mine too. Changed from a Roadrat, largely because the rear mech hanger arrangement on the Rat got tiresome after one too many punctures! It’s definitely a bit sturdier than the RR – I didn’t particularly think the RR was flexy until I rode the Kaff for the first time, but there is definitely less back end wiggle on the Kaff (when loaded). All up weight is about the same though I reckon.
Don’t know if anyone else has the same issue, but I think heel clearance is pretty tight on the Kaff, it does seem to be pretty wide at the backend. If you have big feet it might be something to look out for. Toe clearance is better, I only occasionally catch my toes on the mudguard. Neither of these things were an issue on the RR.
Run mine 1×9, 32T with a 11-32MTB cassette on the back.