I am doing some lab exercises on "OER/PfR" (Performance Routing) and I am just wondering whether this technology is really practical in production? At least in the last 3 environments I worked I have never seen such technology implemented...
Can't really comment whether it's "common", suspect not for serveral reasons, a couple being having both the equipment and environment that might benefit from it.
As to "practical", I've have and am using in a large production environment (multihomed Internet and multi MPLS CEs) and have found it has a few "gotchas", doesn't work exactly the way I want, and might have a problem with link flap knocking it down (at least on ATM interfaces). So there is some "pain" using it, yet I believe the benefit outweighs such pain. However, at least where I've been using it, my view is the minority viewpoint, i.e. the majority believes the effort isn't worth the pain.