On Windows, PTGui's mouse tracking performance was never good, and it has been getting steadily worse. Now in version 12 not only does the mouse cursor often jump erratically and sometimes freeze for seconds at a time, but clicks sometimes fail to take effect. Usually these conditions resolve themselves quickly, but sometimes I have to switch to a different application and back to clear them, and in a few cases have had to abort PTGui.
I won't say that this is intolerable, because I tolerate it. But I paint a lot of masks, and this problem makes that much harder than it should be.
Sure, Windows has never been famous for responsiveness, but nowadays all other apps that I use track the mouse far better than PTGui. Please do something about this.
[My opinion as a s/w engineer is that the problem is likely in the handling of the Windows message queue. By default, mouse events are delivered on the same queue with a zillion others; parsing them out can take a lot of time and when there is a complex stack of message handlers they can even get lost. But there are options to deliver mouse events to an app more directly, bypassing the big queue. I suggest you look into that.]