Final Firefox 17 for Windows, Mac and Linux is out today 

we see the proper desktop version of Firefox get updated to ver. 17. The version spent about a month at beta stage, available to everyone interested for testing.The new version of Firefox doesn’t have that many new end-user features. One change is the way it handles older versions of plugins such as Flash, Silverlight, or Adobe Reader. If you have an older version of these (perhaps because you don’t have enough user rights to update them), they will be temporarily disabled until you explicitly allow them to run for particular elements on the page via the so-called Click-to-play interface.Mozilla Firefox 17 brings along several other changes besides the click-to-play for blacklisted plugins. 

Here are some of them :

Updated Awesome Bar experience with larger icons  

Mac OS X 10.5 Leopard is no longer supported  

Web Console, Debugger and Developer Toolbar faster and easier to use  

Over twenty performance improvements, including fixes around the New Tab page  

Social API is now fully supported along with Facebook Messenger for Firefox