I use Graphics Gale only.
1) Customizable hotkeys for all functions- look under preferences.
2) Loupe: a zoomed in cut of the area around your mouse. Zoom roughly customizable.
3) Preview: Shows your image and animation if any, at customizable zoom and display rate.
4) Single pallet: Work from a pallet which is kind of locked. Changing the color in your pallet changes all the colors of that in the picture. Used in .gif format.
5) Alpha channels: I haven't really looked at this, because I don't use alpha in pixel art and I have PSE. But you can handle them with set opacity, additive opacity, and erasing.
5) Anti-aliasing: Optional on text and resizing selections.
6) Scroll: Move all pixels in selection with wrapping vertically or horizontally.
7) Edit a variety of file types: .ico files, windows cursor files (.cur), windows animated cursor files (.ani), and .avi files.
Built in browser: Can give previews for any supported file type, show supported file types in all sub directories, and have animated previews on animated files.
9) Color counter: Shows you amount of colors in current layer and frame.
10) Onion skin: Optional with forward frame, backward frame, or both.
13) Adjust colors: adjust brightness, contrast, gamma correction, red, green, blue, saturation, and save presets.
14) Text: Optional borders and pitch among the usual features.
15) Batch conversion: Mass convert files.
16) Basic tool hotkeys: Right click for select color (+control for secondary), right click and drag for rectangle selection (in any tool but rectangle selection), control click and drag to pan view. You can choose to have SPACEBAR or ALT put a popup menu with all the tools by the mouse.
So yeah, I really like Graphics Gale.