My admittedly limited exposure to whole program optimization has essentially only given me the impression that it’s ridiculously slow. These are impressions from reading about MLton (ML) and Stalin (Scheme). Given that backdrop (which as far as I know is the default in those circles) I would’ve expected any improvements in that regard to be mentioned in the promo bits, but it doesn’t seem to be there.
With that in mind I think it could be easy to make compilation of PureScript prohibitively slow by running it through a whole program optimizing compiler. ML in general lends itself to fast compilation but they even managed to make that slow.
It’s definitely really cool, though, and I really like the idea of getting a sort of re-targeting for free with it.
Edit: I guess in the end it’s really only an issue of someone / people doing it if they really like the idea and yay, benefit for everyone, as long as it doesn’t disrupt the core.
Edit 2: I guess I should revise this because obviously as long as there’s parity, development can be done with fast compilers and releases built with slower ones, so I’m not sure what I said is valid.