I have released 0.25.0 on Monday.
Contrast Tool
A new feature that was included is a contrast slider in the enhancement tool, moving on with integrating patches hanging around on Bugzilla for quite some time.
SSL certificate handling
A second enhancement that was introduced is the option to override invalid SSL certificates. This is currenly only available in the Piwigo publisher and might be added to Gallery3 in future, i.e. all services that might be self-hosted on self-signed cerfificates.
Enhanced ACDSEE support
0.25 introduces the support of reading ACDSEE’s proprietary image tags such as titles, categories and hierarchical tags!
If you want to try it, there’s a new, unstable, PPA for Shotwell at https://launchpad.net/~yg-jensge/+archive/ubuntu/shotwell-unstable