0.15.x was the release of HACS (to date) with the most patch releases ending at 11.
Most of the reason for that is the new experimental UI, which I had planned to ship with this version (read 0.16.0).
That did not happen, however, if you were using the new experimental UI, you will no longer see the old one.
The new UI will most likely be the only UI in 0.17.0 when that is released.
Even though not much has changed in the integration itself, a lot around HACS has changed since the release of 0.15.0, here are a few highlights:
HACS has a new home 🎉
HACS has now moved out of the custom-components org and into its own, the reason for that is that HACS became too big to have it in just one repository.
You can find the new GitHub organization for HACS here.
The new documentation site went live https://hacs.xyz
There is now a Discord server for HACS
@HACSIntegration is now on Twitter.