One of our computers has been slowly rotting for about the past four years. It was running services like RADIUS, DHCP or DNS and also acting as our backup server. After it started showing signs of severe madness, we acquired a replacement machine.
One of the problems with the old machine was that the disk drive used to store our backups wasn't in a RAID of any kind, which turned out to be quite truoblesome since it's the one that started failing. Therefore I decided to put everyting on a RAID1 on the new machine and also stash LVM on top of it -- that's a combination that's been working out quite fine for us on our other servers.
I remember reading a few years ago that it was impossible to have everything on LVM including /boot. However, these days it's quite possible and I was somewhat surprised by how simple it was to set up, considering that all tutorials and HOWTOs I found on installing Debian or other Linux onto LVM instructed people to create a separate /boot partition which would't reside on a logical volume.