Hi,
I got the APC 42 as a christmas present, and after a month I can say that I'm very pleased with them. I haven't had glare issues, at least in my use cases, mainly in the forest and for astronomical use. In my opinion the weakest point is the considerable amount of CA, but that was somehow expected for an achromat fast objective at 16x. The IS, in my opinion the IS is very good, better actually than the IS of the Canon 15x50 (see below)
I have had some months ago the canon 15x50, and as far as I can remember, they were a bit brighter (expected), a bit flatter and with less CA. But eventually, I had to sold them, because maybe I'm too sensitive to the temporary blurring or defocusing of the vari-angle prisms. In the end, I found my self continuously re-focusing, and that problem made the canons unusable, at least for me.
I have also the Canon 8x25 IS, and they are a real little gem. Optically quite good, and the IS is the best I've tried, is like they are really mounted in a tripod. No blurs, no defocusing. I'm tempted to try the 10x42. Although they have also the vari-angle prisms systems, nobody is reporting the same blurs of their 15x and 18x siblings.
I have to confess, that I have other 42's (Swarovski EL 8,5x42, Leica UV 7x42HD+) that are better optically, but lately I'm grabbing the kites for my backpack, because in the end, I can see more with them.
Regards!!