But unless Mac OS X becomes as strict about background processes as iOS, third-party applications can still waste energy.

Apple did some lovely stuff with OSX Mavericks that at least tries to mitigate this http://arstechnica.com/apple/2013/10/os-x-10-9/12/

After they added the menu telling me which 3rd party apps were wasting energy I reported bugs to them all and within about a year they had all removed whatever polling code and they dropped dramatically in power usage, today Google Chrome is the only 3rd party app that I use from time to time that drains my battery.