Features

Spatial resolution-independence

Most elements are vector-based, and all layers are parametrically generated, hence even when changing the target resolution of a project, the only pixelation will occur in imported raster images, not the built-in components.

Temporal resolution independence

Animation-keyframes are automatically interpolated by the computer, resulting in smooth motion

High Dynamic-Range Imaging (HDRI)

By using floating-point math in the image calculations, HDRI processing allows canvases to internally understand a far greater range of pixel luminance, resulting in better lighting effects, and improved color composition.

Pentablet-friendly tools

The draw tool already reads the pressure sensitivity channel off your favorite tablets, for natural line weighting, and more to come!

Artist-oriented design

While it may not be obvious in this early state, Synfig (and its proprietary predecessors) has been designed from the ground up with animation workflow in mind.

Built-in CVS support

I haven't tried this yet, but I saw it in the file menu and it looked nifty, so- Hey, feature!

Path-based Gradients

Unlike purely SVG-based vector software, and most consumer-level animation programs, Synfig has full support for gradient paths - gradients that follow along a drawn shape. This allows artists to easily add soft shading to animation without the trouble of painting it onto every frame.

Layers

Synfig supports a multitude of layers of various types; geometric, gradients, filters, distortions, transformations, fractal and a few others.

If you would like to see more features in synfig, please contribute to the wish list.