My challenge is deciding (i) do I work on PHP 5.6 / 5.7 and the
corresponding beta APC version which at current rates of adoption
might have begin to have an impact in the community sometime in
the next 5 years, or (ii) work on a performance patch to the
stable APC version which is typically installed with PHP 5.3 which
these guys could apply within a few months.
or contribute those patches back and integrate them into the vanilla apc?
Humm. I think that we are sort of saying the same thing, but at cross purposes. Of course I should offer any up patches for mainstream APC and at best these will go into 3.1.14 or 3.1.15 and may then get adopted sometime for production systems whenever -- that's only if the release of a core O+ doesn't drop APC into legacy status.
However Ubuntu 12.04-LTS is a good example of a stable production stack and this uses PHP 5.3.10 and APC 3.1.7. Debian Squeeze is even further behind and it runs PHP 5.3.3 and APC 3.1.3.
A performance patch could also be made available based on the last stable version of APC, say 3.1.9 -- that is before the attempts to support the new PHP 5.4 features destabilised it. With this patch, then at least individual system admins would have the option to download a stable version from PECL + patch it to use with their production stacks within the next 3-6 months.
Regards
Terry