As I use it more and more I find more and more frustrating things about it.
First off, if the width or height of your sheet changes at all, all your animations are broken, even if the positions relative to the top left corner haven't changed. This seems unacceptable. If I need to alter my tile sheet drastically, of course my animations can't adapt without an extreme amount of work on GM's part, but if the relative position of those frames hasn't changed, why has my entire animation been destroyed? Hopefully this is just a bug, because it's infuriating.
ESPECIALLY when compounded with the fact I can only do one tile at a time. I have 6 "groups" of tiles that all animate together. Yet I have to define each individual member of the group one at a time? So frustrating, especially when all that hard work is destroyed by the above issue.
Tile animations are an exciting edition, but in their current state, I'd rather use the method described in my tutorial using sprite_assign().