The miles can be used effectively but it takes research. The trick is to forget about Delta flights and use skyteam partners. Delta flights are almost always at "medium" or "high" levels, whereas most partners usually have only one level, which is "low". (for now at least...).

Use the airline route mapper tool (http://arm.64hosts.com/) and set the filter for skyteam airlines and check flights to/from your destination/departure airports to anywhere near your departure/destination. Focus on the major flights (trans-atlantic or transpacific) first, and find some flights that work. Next use KVS or ExpertFlyer (depending on the airline) to check availability of seats in their award classes. Once you find flights and dates that have availability on the partner(s), call up Delta. You'll need to tell the agent to book the award flight by flight, but you'll get your ticket for low miles. In some cases the airlines will be better than Delta, in some cases worse. But this works.