It's readily apparent that the 15th is when the new antispam solution went live partway through the day on segfault, and you can see that the MX propagated out over the next day, and then I modified the mailservers which segfault scrubs for to toss un-scrubbed mail to segfault for cleaning (so that even the spam-systems which hit backup MXes will get scrubbed). The 4.0 baseline on segfault when I wasn't using it after Firan had moved off to its own machine is just the basic watchdog/monitoring tools, and automated update-checking.
Snafu, obviously, has rather higher stats, being the shell/mail/webserver. Still, I find it interesting that now neither is anywhere near hitting their bandwidth limits, /or/ their CPU limits. Overall, I'm quite happy with the setup at ThePlanet. :)