Wietse is out to replace sendmail. If someone has an environment where Postfix cannot fit, because it's missing some important feature, then the discussion will be about how to best add the missing functionality to Postfix and when that can happen, not whether the someone should rearrange their environment to fit Wietse's preferences. Postfix more closest to sendmail that Qmail. Postfix is still really young. But author told that's not meaning that his software is raw.
Postfix uses text files for config.
Master.cf is a table that defines a lot of process-level parameters for the process manager. The most recent is a regexp map, which is the first cut at rewriting support. The license IBM provides Postfix under allows them to remove your right to use or distribute Postfix at any time if they even think it might have stepped on someone else's intellectual property rights. This is clearly unacceptable to just about everyone, and efforts are underway to get it fixed, but until then, it's hard to justify spending a lot of effort learning or implementing Postfix if it could suddenly be recalled. Exim is a MTA developed at the University of Cambridge.