When you give engineers 40mm of space to work in, and say that it’s okay (& now necessary) to change the physiological input-output relationship, you make controversy and uncertainty (who knows what % improvement this gives, and is it the same for all? No) part of the sport.
By the way, don’t bother asking how this shoe is legal, because the Emperor’s Clothes of tech regulation last Friday made it clear that all companies SHOULD do this. Also, at this point, it’s more likely that the regulations are compliant with the shoe than the other way around
Aside from obvious issues of equipment parity and the ability of companies to bridge the gap (as they now must), one of the biggest problems I have is that the more advanced we get, the greater the potential gain, the larger the gap between responders & non-responders becomes
In the first batch of lab studies on the most basic “super shoe”, they found a range between 0% and 6% in physiological benefit (see example). As you make the benefit larger (on average), this spread will go up. Maybe you even create non-responders. This is crucial for integrity 
What it means is that *EVEN IF* all companies achieve the same typical benefit (it’s a big if), runners on the start line will be separated by the spread of responder vs non-responder. So running has a new success criteria: if you don’t get 4 to 8% from the next wave, you’re done
So you could scout for 100 top young runners, but now you have a variable that could separate them by 4% once they all get put into the “best shoes”. In my opinion, that undermines the integrity of running, even if, and I can’t stress this enough, everyone has the same shoe!
This is why for a sport where value is in human achievement & physiology, the rule must limit the scope of what tech can do to the outcome. That’s why a stack height much lower than 40mm would have been a good start. Don’t let a variable ‘outside a runner’ make or break a runner
If this sounds familiar in concept to some of you, it’s because it is - cycling recognised that when EPO use was unregulated and pervasive, some riders got major benefits, others not, and this becomes the primary determinant of success. It’s not sport anymore, is it?
Ultimately, I guess it comes down to what you want from running. I want to know that I’m seeing a result, or a performance in the context of history, that is achieved by human ‘evolution’ or breakthrough. Not by doping, not by equipment or the runner’s responsiveness to it.
It’s the same as when I watch, say, tennis - I don’t want to wonder whether a guy who loses in 5 sets might have won if they'd swapped rackets. And I don’t want to see swimmers win because of swimsuits. But this where we are - weak, passive leadership that has changed the fabric
So we enter an era where shoes like this will be trumped by the next big thing, then the next, and records will tumble (marathon WR to go under 2hrs soon, and track records will be smashed) but without the same meaning, amidst considerable doubt over who is actually the best?
I find it quite sad. One of the great appeals of running was celebrating its history, records, breakthroughs, even PBs outside the spotlight. The limit was set at physiology, not equipment. The distortion of “input vs output”, and loss of integrity hurts the sport massively, IMO.
