No offence taken. Ok, as far as that poll is concerned I guess the reason CentOS wasn't listed is because we know it works on CentOS as it's just a rebuild of RHEL.
I also know it works well as I use CentOS on my own systems. Without going through the whole thread I can't remember if it was meant to be a poll for OSS implementations of Zimbra rather than inlcuding NE.
The simple reason we don't support CentOS (and others) is because we don't want to provide operating system support as well as support for Zimbra. Believe me, that would be the case for a lot of users. I'm sure you are perfectly capable of supporting your implementations of CentOS but many users aren't and as I'm sure you'll also know that providing support is expensive. A company simply can't afford to hold a customers hand and help them fix bugs in their operating system, with products that have a support contract associated with them (the RHEL subscription for instance) we can point them back to their vendor. A recent case that's been prominent on the forums, Debian 3.1 has a horrendous bug in it that cause permissions problems if a process fails. It's caused Zimbra (the product) a lot of problems with all sorts of errors - where do we point the user in that case? It's been a very long while for that bug to get resolved and I'm not sure it has been in 3.1 (but I could be wrong as I don't keep up with Debian).