It seems that Elementary Tweaks is no longer developed. But here comes the power of open source: a new developer, Michael Starkweather picked up the code and continues to develop it. He already released a new version what works well in Freya.
The new version has been slimmed down and has been extensively refactored to be much, much better internally (down ~1000 lines of vala and counting!). It utilizes the newest elementary tools for Freya and the Freya libraries.
If you already use Freya, you can safely install the new Elementary Tweaks by typing the following lines to Terminal.
sudo add-apt-repository ppa:mpstark/elementary-tweaks-daily sudo apt-get update sudo apt-get install elementary-tweaks
After installation you can see a new Tweaks menu in Switchboard control panel. If you tried it and found a bug or want a new feature, please report it at the project’s Launchpad page: https://launchpad.net/elementary-tweaks.