$99 is steep for an upgrade to a plug-in...
Overall I prefer Convert to Black-and-white Pro.
So far it seems to be the PC folks having problems, not the MAC folks.
If that's the case, could be a PC-only issue. Time will tell. But one thinks they would have tested it thoroughly on both platforms before releasing it. I note they have no public beta program. Perhaps they should consider doing this in the future, because it nets-in a much broader variety of user conditions than they could possibly recreate themselves in their lab.
I don't know the extent of your awareness about what it takes to redevelop software, but this is a big, costly undertaking. They weren't only adding features, they were re-writing code to improve basic processing efficiency. When you start doing that, it's like re-working the app from the ground-up for at least two platforms if not more. That consumes a lot of labour and overhead, which needs to be paid for out of EXPECTED future sales. So the price is the price. They have no interest in shooting themselves in the feet over-pricing software, nor do they have an interest in losing money on every copy sold. So it depends on whether the price is worth it to us the customers. It has enough new features that I bought it. Others MMV, but don't buy it and then complain about the price.
As for Convert to B&W Pro, yup, in its day a great piece of software, but Nik SEFX Pro just blows it out of the water in so many ways.............time to move on.