Phew! The big re-arrangement to decommission the venerable F630 Netapp is finally pretty much done. Now we have a new beefy fork, a dual-Opteron screaming along as the main mail and CVS server (running the OpenBSD/amd64 port in SMP mode). Quick takes up the web serving duties, running thttpd and Apache. Hidden away from public glare is "chunk", serving up 400Gb of storage for backups and "multimedia content" to both machines.
The speed increase from removing NFS from the equation has been pretty incredible. Maildir is a nice format, but it really needs a top-notch NFS client to avoid dying from opendir overload when users have tens of thousands of mails in a single folder. Not to mention the locking headaches that NFS introduces as well (on local disks, Dovecot can now use its index files much more effectively). Overall, I'm pretty happy with a local disk / rsync combination until some maniac steps up to improve OpenBSD's NFS client to Solaris or FreeBSD levels.
On the software side, things have really improved regarding 64-bit cleanliness, and only one package, maildrop had a problem - it uses C++ exceptions which aren't supported by the amd64 toolchain on OpenBSD yet. A swift switch to procmail later, all worked peachily. qmail doesn't compile out of the box, but the excellent netqmail patchset integrates fixes for this. Only outstanding task is to bootstrap ezm3 on amd64 in order to run CVSup (or perhaps cvsync would be simpler).