My reason for using LVM is that I reinstall, upgrade and generally mess around with my OS installs so much that I have found that LVM gives me fantastic flexibility in moving, expanding, cloning and backing up my OS partitions at my leasure without the risks assosiated with other partitioning methods. It does, however, make multibooting your OSes a little complicated and unpredictable at times, especially on newer hardware, where the process gains another level of complexity.
What I'm talking about are the new UEFI (as opposed to BIOS) motherboards, which allow you use the full potential of, and to boot from, 3TB+ hard drives (when formatted in GPT as opposed to MBR). Things can get incredibly complicated and messed up because each time that you install a new OS on your machine, it will overwrite the EFI bootloader (.efi) files of your previous install and you will end up with a series of broken entries in your EFI "BIOS" bootlist and a load of pretty much redundant grub bootloaders scattered about your partitions. This offends me on so many levels, not least of which aesthetically.