Tonight I used a Derby DE blade for the first time. While it gave me a ok shave thats about it, just ok. The soap that I used was my normal D R Harris cream. I've been using the Crystal and the Personna Red both from Israel and I really like both of these blades. The Derby didn't seem as sharp and sort of dragged although I did not experience any razor burn. I can not imagine the Derby being suitable for more then one shave only.
Jim