Official thread can be found here:
ACE has been in testing for quite a while, and releases are kept private for testing purposes quite extensivly.
However as it is a work in progress the releases are still considered to be in beta stages, and in the end it's up to the administrator if the server is to be protected by the anticheat or not.
Most admins including developer try to maintain support for those having issues, and as quite frankly the difference between UTDC and ACE are enormous.
Looking forward to try answering any further questions you might have.