In my experience, there are two ways the ESC key fails. The first is trying to abort any command that is non-instantaneous. maybe an intersect, maybe a make2d, a patch, anything that involves a lot of objects. in short, anything you might want to escape from (most likely because you didn’t realise it was going to take so long)
the other fail is something that happens less frequently, and which is more likely an incidental effect of a larger fail - ie the complete freeze of rhino when trying to do what should be a very simple command - an intersect between two or three simple objects.
I have had this happen on two or three different computers, and my colleagues also have the same issues. my current machine is a high end i7 macbook pro with 16gb of ram. the amount of processing power or memory seems to make no difference. once you’ve started a compute intensive operation, the ESC key fails to abort. I run both windows and macos on the same machine, and the windows version of rhino has never had this problem. I should also note that I mostly use the WIP version of Rhino for mac, though the problem exists in the release version just as badly.