It works fine with me and I have 2 ez sites running, one with caching off and one with caching on. It took page load time from ~0.9 seconds with ez caching on down to less than 0.2s with ez caching on.
I think with apache 2 (and 1.3???) virtual hosting you can use different php.ini files for each virtual host. Look into that for the ability to turn on mmcache one site at a time.
