Ron,
Good points, and I totally agree that it must be a very good cartridge. As you said, it equals the great 416 Rigby performance, so it must be good.
I think that one day, somewhere in the future it could possibly become a "fad" cartridge, you know, a flavour of the year cartridge, then things will be different and everybody will want one.
No doubt if that happens, it will perform very well in the field for those who put their faith in it.