Another reason NOT to use the "Auto Delete" after ingest just happened to me last weekend:
2 NEF files out of about 600 got corrupted during ingest on both the main and secondary location on the PC (was visible on the tumbs in PM). Neither version would open in any software (Capture NX2, View NX2, PS CS5, PSE 7, Phase One). Luckely the files were still on the card and not corrupted, so I manually copied them once more. They work fine now.
This happened only twice now in the 4 years I use PM, but when it happens it's a pain in the butt ... and you are glad you still have it on the card.