"Seems Theo was looking at this a decade ago so I guess OpenBSD is already okay."
AFAICT those OpenBSD fixes related to an unpublished change w.r.t bits of page table being cached when previously they were not. I think it would be dangerous to assume those fixes also cover Meltdown.
The points Theo made about the errata preventing people from implementing secure software remain valid.
As I've said before folks really should look at the errata before purchasing a CPU - it is shocking just how broken some of them really are. That won't always help though - case in point try tracking down all the errata that Theo talked about (eg: AI90) 10 years ago... You may well struggle - because Intel's policy is to unpublish errata after they've made a fix/spec change... If anyone does find those errata - let me know. ;)