Since many years I investigate on out-of-the-box FreeBSD upgrade procedures which especially allow one to upgrade a FreeBSD server fully remotely via an SSH connection and without console access or even single-user requirements.
The ultimative killer procedure here certainly was the FreeBSD 4.x to 5.x upgrade procedure which used a hard-core in-place system overwriting approach in order to avoid the usual requirement for console access and single-user mode. Hence it was suitable for upgrading a server in a Datacenter remotely via just SSH access. It was successfully used to upgrade many dozen FreeBSD servers in production environments.
The recently developed and used FreeBSD 5.x to 6.x upgrade procedure again was a more simple one. This is the procedure which is currently in use when moving to the latest FreeBSD-STABLE. It also was used upgrading about two dozen FreeBSD servers in Datacenter environments.
As FreeBSD 7-CURRENT fast approaches the RELENG_7 (aka 7-STABLE) branch now, I thought it is time to finally provide a FreeBSD 6.x to 7.x upgrade procedure now, too. It is still not tested as well as the other procedures. But this will be changed on-demand over the next months, of course.
In case you want to just try out FreeBSD 7, please directly install FreeBSD 7 via one of the snapshot ISO images. But if you want to upgrade an existing system, then this new upgrade procedure might safe you some hassles. Hope it helps you, too.