[qalmakka]

I have not seen crashes, but I often saw corrupted DPKG databases. This is very rare if you stick to upstream repositories, but it gets more serious when you start mixing third-party repositories in (i.e. I saw people replacing GCC with newer versions from outside repositories, and due to the sheer amount of stuff depending from it, doing a dist-upgrade required purging an immense amount of packages). I must admit it's not usually an issue on servers, though.

[hiq]

This doesn't seem related to apt vs yum, rpm etc. but more to replacing essential dependencies by third-party versions. What happens if one uses the same kind of hacks on CentOS? Does it handle these better?

[qalmakka]

In my experience, RPM is a bit more resilient to this kind of stuff, because I've never had such a problem on SUSE or Fedora. CentOS is different, because tecnically you're not supposed to upgrade it to a newer version, so it has less chances to experience these issues.