Dear Karl,
Working my way though the list on program-transformation.org, and checking references (publications, manuals, available downloads) for the systems, seems to suggest that "reasonably mature" systems might include ASF +SDF, DMS, Elegant, FermaT, Stratego/XT and TXL, but I'm sure there are more.
I think you can add Tom (http://tom.loria.fr) to your list. It is not as "high level" as ASF+SDF or Stratego for example. On the other side, it allows you to develop a Java application, using associative pattern matching and traversal-strategies. Using ApiGen, Tom can be used to transform trees/terms produced by SDF.
kind regards, Pierre-Etienne