This software is perfect for sprites, animations and tiles. It is very solid and stable, and works like a charm. Even though in early development (pre-1.0) the features present are many. It has support for multiple layers per frame (and not the usual layers = frames), which is already better than most free pixel art editors. Plus some very nice features like screen splitting to allow editing many files at the same time seamlessly! Some features are somewhat hidden, so you'll have to learn shortcuts and browse the help a bit, but after a days work I already felt at home. The developer is very active and has assisted me with a bug on the mac version (couldn't open ASE) personally. In less than a day I had a working copy! Check it out for yourself :)