Along with assorted bugfixes and performance improvements, the following major issues have been addressed with this release:

Added support detection for the following image types: jpxr, jpg2000, and apng.
Image format support can now be handled using extensions. SVG and WebP remain a part of the Picturefill core, so as not to break existing implementations.

Support for intrinsic image dimensions
Picturefill now matches native behavior in terms of an image’s inherent size: when served at “2x,” the image is displayed at half of its source’s inherent size. Note that this can and must be overrideable via CSS.

Picturefill is now a named AMD module, and uses AMD/CommonJS module factory also in native supporting browsers.

Picturefill has a team now
Everyone join me in welcoming the team responsible for the lion’s share of work that went into this release, and many more to come.

Did someone just whisper “Picturefill 3?”
I thought I just heard someone whisper “Picturefill 3.” Weird.