I fitted 4 KU31's on the old 'bus, fully expecting them to not be as good as the F1 Assymetrics on their previously of course, but since it's on school run duties, optimal performance wasn't high on the list!
Although I can understand people having the "not wanting to admit they bought crappers" syndrome, but that's not me at all, I bought them explicitly expecting them to be crap, but wanting to at least try a set for myself, so I could use my own judgement to see how they stack up, and putting them on the school run wagon seemed a no-brainer at the time.
Oddly, they aren't as bad as I as expecting, and actually since I like to throw the 'ol bus around on the limit when I'm in it on my own, I am finding the KU31's better then my F1A's.. Namely grip levels are as good if not better in the dry, they seem to be much more stable on the limit, and despite expecting wet weather to kill them, they seem pretty decent in the wet. Even responsiveness seems the same, although they are re-inforced (92Y), so not sure if that helps at all, the Bus has the active dampers, and always has this almost artificial very quick initial turn in response (but it's weight obviously overcomes that soon after), and that is still present, I don't find them sloppy at all.
I totally agree that different tyres on different cars behave differently, and more importantly re-inforced versions behave quite differently to non-reinforced since their construction is totally different and inherently you'd expect them to be 'sharper'/less compliant, but at least for me, I can say I've tried the cheap option (hardly 'cheap' though, £90 instead of £130 is only £40 a corner cheaper (225/40/18)) and they do live up to the hype for me, so will get another set on the car once these are through. I can say they are in this size/type noticeably better then the FK452, which my brother had on his 300BHP Bus..