Synfig is a powerful, industrial-strength vector-based 2D animation software package, designed from the ground-up for producing feature-film quality animation with fewer people and resources. While there are many other programs currently on the market to aid with the efficient production of 2D animation, we are currently unaware of any other software that can do what our software can.

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.