I'm very much a proponent of using non-core references, and even references to things that haven't been updated yet. It's a shame when a replacement deity has to been chosen for a monster, for example, just because said deity hasn't made a 3e appearance yet. I love the fact that the FC1 mentions draedens, foo creatures, etc., despite the fact that they haven't yet received 3x stats. I also like when spell-like abilities that make perfect sense from a creature, but don't happen to be in the PHB, can be included with a simple replacement or a short sidebar, such as in FCII.