apt-proxy has become an omnipresent tool in Debian-based environments. Both in work and in my clients I usually install it so we have a great way to save bandwidth (in a Country where a 512 Kbps ADSL line costs you around 50$/month, it matters) I have noticed also several Ubuntu users using it, even in big environments where a local mirror might be justified and even when other solutions like apt-cacher seem to be getting stronger.
Sadly, current state of apt-proxy is not so good (see bugs 282746, 316670, 274679, 262528, 327268, 302503, 295329 and probably others). While upstream is doing a great job implementing fixes, the user base has evolved very quickly and it’s starting to find (and fix) bugs by its own. One example of this is the current release of this version of apt-proxy, made by Daniel Baur, which implements pending patches for eight bugs, including patches which solve Ubuntu-specific issues.
A partial debdiff which shows the relevant changes on the code is here for the lazy admin. Chris Halls has acknowledged these fixes and plans to upload a new version to Sid soon. That would be a happy-ending chapter of saving apt-proxy from death. Personally, I’m going to have a closer look on apt-cacher while this new package appears.