My most enjoyable time in minecraft other than building weird auto-farms and massive crystal structures is spent in looting mineshafts and strongholds. I then use the loot for further construction projects.
In a new SPS world The first stronghold I found was really miserable. Other than the Portal room there were only 3 small stairs, about 40 blocks of finished corridors and about 15 blocks of an area having only a floor layer of block, not really a corridor. Portal room and unfinished area did not even connect to the other section. The Portal room was at level 6 and the top of the ceiling of highest stair was only level 24. Nothing else, as in Voxel Map cave mode I scanned from bedrock up to surface at widest range possible.
Total loot from this crummy place was only 60 iron bars, most of them from the portal room, and 2 iron doors. Really a let-down. Have to look up some more of them to see how they turn out.