The technical aspects mentioned in the article are more serious.
When using the Move tool, Instead of moving the selected layer by default, the option checked is "pick a layer automatically" which never does the job.
Text editing its a pain compared to photoshop.
Lots of filters dont have a real-time preview, which make applying them a futile exercise of guessing
Layers have bounds that doesnt correspond with the content of the layer (maybe somebody finds this useful, I hate it)
The plugins for Layer effects are all a mess and its easier to do it by hand
Its impossible to select a group of layers, and I dont mean to apply some filter or edit them, I mean to organize the layers. Move up a group, etc. There is no way to create folders of layers... There is no way to hide/show a group of layers...
All this kind of quirks make the program anoying to use for big projects, and I hate it because its completely capable of getting the same results (at my level) than PS, it just takes a lot of time because the UI...