But what of complexity in other popular MTAs? Take a brief look at how you configure virtual e-mail domains and aliases with Qmail and tell me that Sendmail is more complex. In fact, don't. Qmail is fantastically simple at some simple things, yet needlessly complex with others. If I never have to write another script to spit out .qmail-xxx files, it will be too soon.
Postfix is a viable alternative, marrying some of the better concepts of Sendmail to a simpler (and less malleable) configuration. In my mind, it's the only real competition to Sendmail in terms of features and overall ease of operation. One of the main reasons I haven't bothered with Postfix in the past was the lack of milter support. This meant that using milters such as MIMEDefang, milter-greylist, and others wasn't possible. However, Postfix finally added this support in version 2.3.
And then there's the gorilla called Exchange. To anyone who grew up with Sendmail or Postfix, Exchange is an abomination from an administration standpoint. It's gotten slightly better over the years, but I still groan every time I have to deal with it. It's slow and cranky, and the GUI management makes Sendmail's configuration seem like child's play. Say what you want about non-Microsoft MTAs, but one thing they all have in common is that there's generally only one or two places to look for the entirety of the MTA configuration. With Exchange, it's all over the place, yet somehow all within one MMC tool. Exchange is more than an MTA, granted, but that's no excuse for the hoops that admins must jump through to do what should be relatively simple tasks, like migrating to a new server.
Another case in point: A Sendmail-based server with the dovecot IMAP and POP service running needs to be migrated to new hardware or a VM. This task requires building the new server; copying over the contents of /etc/mail, /etc/passwd, /etc/group, and etc/shadow; and running rsync on the mailbox folder. If there's centralized authentication, it's even simpler. All told, that's about an hour's work from starting the OS installation to having the new server up and running. With large mailboxes, rsync might take a bit longer. If it's a Cyrus-based IMAP/POP server, a few more tweaks will be needed, but overall, it's a very simple, straightforward situation.