IGP metrics on WAN links

Just curious as to what people are using for metrics in their IGP
and what their reasons are; bandwidth? geographical distance? latency?

We have a survey paper on techniques for setting IGP weights

  error
  http://www.research.att.com/~jrex/papers/ieeecomm02.pdf

and a longer version

  http://www.research.att.com/~jrex/papers/ieeecomm02.long.ps
  error

that might be of interest. We discuss how to tune the IGP weights
in a systematic, automated fashion based on measurement data (of
topology and traffic) and an optimization algorithm, and show that
good weights settings allow IGPs like OSPF and IS-IS to perform almost
as well as optimal routing schemes that have complete flexibility in
selecting paths for the traffic.

-- Jen