So, I'm working on a project that has some big textures and recently I decided to split into different atlases by scene so that when navigating through scenes SpritKit can get actually rid of unused textures
(Since I cannot control memory usage manually I hope SpriteKit is smart enough to know when a texture atlas is not being used at all and release it if required).
Now, after doing this change i went to take a look at resulting atlases and to my surprise their size isn't a power of 2, which was one of the first things you learned in Cocos2D. (ie. a texture of 540x540 would actually end up being a 1024x1024 in OpenGL so that it makes more sense to be 1024x512 if possible or even fill as many sprites as possible to not waste memory)
If this the same in SpriteKit or any idea how it actually works? Maybe it'd make more sense to not split atlases since I'm going to end up maybe using the same or even more memory with the awful atlases that have been auto-generated...
This info is looooong outdated. Textures no longer need to be strictly POT (exception: PVR compressed textures have to be POT). NPOT was first supported by iPhone 3GS.
These days it is recommended not to use POT textures when you don't have to in order to conserve memory.