My killer-app use-case for LVM is doing upgrades to a new root, while preserving ability to boot to the old. I snapshot my existing root, then clone it onto to a new root LV. This allows me to preserve my old root, and be able to fallback to it should something go wrong with the upgrade (which it does - Fedora Linux, perhaps Linux generally, seems to be getting ever more finicky about installed versions of initrd, kernel and inits).
Without LVM, I'd have to do the upgrades in place. With the risk of being fscked if it goes wrong. (Yes, I should burn recovery CDs in advance - Yum upgrade fails catastrophically infrequently enough that I often don't, but frequently enough though that I have lost day+ to reinstall and reconfigure more than once).