Do you mean at high zoom levels, like over ~2000%?
All zoom levels. When I spin the mouse wheel a number of clicks it redraws every intermediate zoom with a half second delay for each. This isn't helped by the apparent linear scaling of zoom steps. Exponential scaling is most desirable for me (eg. 0.25, 0.5, 1, 2, 4, 8, 16, 32), or step through a custom list of zoom levels like in GraphicsGale.
If this isn't normal behaviour then it might be that I'm running it on linux by way of Wine, given that Air has been abandoned on linux. If only this were ported to Haxe for a native linux build.

How do you mean? You can place a number of instances of a tile and edit it seamlessly. Press W or Tab to see placed tile indices.
I didn't think of that and it's workable, but you've still got to replace those instances for every different tile you want to edit.
The ideal would be to toggle repeat mode and have the image view filled with the repeating tile and edit it seamlessly.