the tray icon is broken

I confirm the bug

Me too. I am also on Ubuntu trusty 14.04.03

Same here. Ubuntu 14.04.3 LTS

Revision 12 was mistakenly built for other releases than 15.10. So I removed it from the published packages of this ppa.
Please remove and re-install the package (revision 11).
See https://launchpad.net/~indicator-brightness/+archive/ubuntu/ppa for an overview of all available packages.

I've updated indicator-brigtness for my elder 12.04.5 and it stopped worked completely. Version 11 is no longer available, had to use the version for 12.10.

Probably you need more clean-up of the repo.

@Ilya G. Ryabinkin (ileyka) I don't understand, nothing happened to the older packages as you can see here: https://launchpad.net/~indicator-brightness/+archive/ubuntu/ppa

I'm looking up here (where, I believe, apt-get is searching for packages):
http://ppa.launchpad.net/indicator-brightness/ppa/ubuntu/pool/main/i/indicator-brightness/

there are no

 indicator-brightness_0.4~bzr11~ubuntu12.04.1_all.deb
 indicator-brightness_0.4~bzr11~ubuntu14.04.1_all.deb

packages anymore, though the corresponding *.gz and *.dsc still exist. To me that means the repos is screwed somehow and you need to repair it.

Re-installing for 14.04.3 does not fix the issue; after removing and then reinstalling using the PPA the icon cannot be found.

I have downgraded the package in a wink after the upgrade, as I have immediately noticed the issue.
Mine downgraded works as it should be.

But now apt system has still been offering the update to 0.4~bzr12~ubuntu14.04.1 after your fix.
It's not listed in an overview but in the index.
http://ppa.launchpad.net/indicator-brightness/ppa/ubuntu/pool/main/i/indicator-brightness/

Erwin fixed the issue, a (hopefully) working version for all Ubuntu versions is waiting for you in the PPA.

I can confirm. I activated the PPA again, update came and the icon is still shown after reboot. Thank you very much for the fix and the indicator itself!

I confirm the new revision 18 has no issue. The tray indicator is shown and with the proper icon.
Thanks a lot.

Back to full functionality in 14.04.3! Thank you so much!