It’s been a very long time since we released a new version of the Add-on SDK, primarily because since Firefox 21 the SDK’s modules ship with Firefox itself. This new version’s purpose is mainly to update cfx so that the xpi files it creates do not bundle the SDK modules by default – in 1.14 you would have had to use the –strip-sdk option to achieve this.
One instant benefit of moving to this new default is that xpi files are now much much smaller, as small as 8kb! As well, as the xpi only contains your code there will be no problems with ‘outdated SDK version’ warnings with the AMO validator.
You can download SDK 1.15 Beta 1 as either a Zip file or a Tarball.
Please take this new version for a spin and let us know if you have any
issues, either on the mailing list or by filing a bug.