The TSA has settled the confusion about whether you can take DE razors (& blades) on commercial aircraft flying in the US:
Because these razor blades are so easy to take out, safety razors are not permitted in your carry-on luggage with the blade. The blades must be stored in your checked luggage.
Cartridge razors are OK for carry-on. A DE razor without blade is OK for carry-on. DE razor with blades is NOT OK for carry-on.
Full text here.