>Is there any point in starting testing of 2.5S3 + all patches now, or >should I just wait for STABLE4 to be released shortly?
Squid 3.0 recently entered its release cycle, so there may not be a 2.5STABLE4, but a 3.0STABLE1 instead. I'm not a developer, so I can't say for sure. If you haven't already, you could search the squid-dev archive to see if there's any reference to 2.5STABLE4. Adam