After 2.5 years, there's finally a new release of ZDoom and a new ACC to go with it. Visit the download page to get them. There have been significant changes to ZDoom over the years, including:
Mac OS X
The OS X version of ZDoom now features a native Cocoa back end that significantly increases performance, in many case doubling frame rates, and is also more stable than the previous version.
Linux now uses SDL2 which can produce less frame jitter with high frame rates, has some vsync support, and fullscreen is now a "desktop fullscreen" mode.
ZDoom already worked great on Windows, so nothing has changed here.
A fairly complete list of changes since 2.7.1 is available on the wiki. I'll probably pick out some highlights to list here eventually.