I’ve been using AdobePhotoshopSketch for a while now (two or three years, maybe?) and its REALLY GOOD. Of course it has its downsides, like limitations on certain things such as the layers and brush sizes, but otherwise, its great. Besides, its free.
At the same time, there are some features I would like to have. For one, it would be really nice to have a fill/paint bucket tool. It’s really time consuming to finish the line art of a drawing then having to create a separate layer to color in everything. With something like that, 15 minutes of base coloring turns into 30 seconds.
I don’t really have a problem with the layers because I never really use too many, merging some together whenever I reach the limit. However, I’d really love the zoom to be bigger. I understand that adobe sketch isn’t a vector based app (at least I don’t think it is...), but when I try to add detail to something, the limit to the zoom is pretty unhelpful.
Nevertheless, if you’re looking for a fairly high quality art program for the minimum price, I suggest Adobe Sketch.