What a gigantic HEADACHE. I can see how it can be useful from an administrative standpoint and how it is tailored for RAC, but I am skeptical of the supposed "performance" increase. If it slightly increases performance, is it worth the headache it causes from a configuration and maintenance standpoint? To me, absolutely NOT. It takes a DAY or more to set it up and configure it correctly. This is BEFORE the DB software is installed/configured, and the database being built. Using regular SAN LUNS, I can partition, mount, and be ready to build the database in ~30 minutes. ASM is not worth the headache to me.
Why would I want a SECOND Oracle instance just to manage my DB storage disks? That's more CPU and memory being eaten up just for storage purposes.