Yes, there are others. I haven't tried the ATI, but this question has been asked and answered more than a few times on this forum (and others). I have taken the impression that the ATI has just a few more dissatisfied users reporting than some of the others, e.g. the S&K and the Armalon. But there are also satisfied users reporting on the ATI. I suggest you do a search (and note the default setting on the search is for threads in the last week, so change that,) in this forum and also in the milsurp and in the optics.
I use the Cad-Technik, which has good points I like and bad points that don't matter to me as much as to some. But I think it isn't as easy to find in Canada.