I think I'd go with Velocity Aerohead, Fusion, or Synergy rims if I were going to be doing light touring or carrying panniers. You can build a nice set of wheels with Open Pro rims and 32 spokes, but stronger rims (that weigh just a tiny bit more) would give you a margin of safety for potholes and rough roads.

Check out Peter White for Velocity rim descriptions: http://www.peterwhitecycles.com/