play through a whole box of Generation D whistles (20-30 as I recall). The differences were very very small. I did end up buying one I thought was "the best", but any one of them would have been great. All of them were better than any Walton, Dixon, or Clarke I've ever played, and better than some of the Feadog and Oak whistles I've played and/or own. I find Feadog and Oak whistles to be much more variable, but that's just because I own a couple of each that are markedly different in tone and playability. The so-called variable quality of Generations (at least the D ones anyway) is somewhat overstated in my experience.
That has been my experience as well. The whole Generation things has become a sort of an internet trope, floating around the echo chamber.
Yesterday, in the real world, there was a conversation, and expression of frustration, about comments posted (on piping forums but this equally applies here) by 'experts' who have been playing 'all of three months'. Don't believe everything you read was the take-away, unless you can gauge who is writing and from what experience.
Anyway, my most recent experience going through a batch of Generations was that 99% were decent, serviceable and some were great but the differences were mostly of taste and a beginner or intermediate player won't most likely even notice them.
I have not tried or bought Oak in over twenty five years or so, the one I have is a nice whistle but manufacture has gone through different hands a few times since so I can't speak to their current state. Variability comes with the injection moulding process, so I would assume Oaks are no different in that regard from other makes using the that mode of production.
Feadógs come individually wrapped so there's no trying out. The luck of the draw. I have come across serviceable ones and others less so. A Feadóg Pro bought directly from Feadóg Teo was probably among the worst examples of mass produced whistles I ever had to deal with. Binned the head, tube lives on with a head transplant. In general I find Feadógs to tend towards an unpleasant high end. Harsh.
I never found a properly working Clare.
Also note Robertunes' rant was probably triggered by a recommendation for a Cillian O Briain improved Generation (he did make them but not recently, as far as I know). All said and done, I think it's hard to beat Cillian's work, two of his 'improved' Feadógs are close at hand in my house, the go-to whistle, FWIW.