There are at least two problems (or, at best, perplexities) with IIQM.
a) Mental-physical dualism: IIQM explicitly relies on a dualist conception of the world.
b) Absence of correlata: in IIQM, correlations and only correlations have physical reality.
IIQM faces a major objection, nevertheless, because of the way in which it deals with probabilities.
Moreover, as established by requirement (6) of section 3, the notion of probability that operates in IIQM must be that of objective probability.
This constitutes, then, a serious objection to IIQM.
We can take a further step, then, and give IIQM one more shot by assuming that there exists such a notion.
And, in particular, this relational account of probability allows (allegedly) for a consistent IIQM approach to the theory.
2] measuring "spin down", exactly like IIQM predicted.
Second, the plausibility of IIQM depends, as Mermin pointed out, precisely on our discovering a reasonable account of objective probability.