We'd like to use MMCache, but the latest version of it has been released so long ago. Is it still developed? Are new versions of PHP fully supported?
It basically died and resumed by eAccelerator a while ago.
"eAccelerator was born in December 2004 as a fork of the Turck MMCache project. Turck MMCache was created by Dmitry Stogov and much of the eAccelerator code is still based on his work."
and APC is still very much alive and will probably be embedded into PHP6 so it might make sense to hop on the bandwagon early :)