Glad Derbys worked out for you! For me they are mediocre at best. Just shows YMMV!
I think one can make peace with Derby, while still regarding them as mediocre. I developed a dedicated "Derby technique and prep" for being able to use them effectively. They are still my worst blade for that. But, let's say that now that i can at least use them, they are much closer to my 2nd worst blade, the Supermax super stainless. The Supermax is sharper, but it has a sort of rough glide. The Derby is duller, but it's so dull, that is very smooth and glides easily, once you use the "Derby technique" to avoid the tugging propensity.
I find that all blades, have their uses at the end. You had a weeper or nick last time or you want to shave ultrafast and don't care about BBS? Load a dull blade. The not as close of a shave, will avoid any new weepers, heal your skin and you can do that fast. You want to chase BBS and shave at a normal pace? Load a sharp blade and take your time...
Plus, shaving with your worst blades, makes you appreciate next time, all your better blades more. Because if you shave every time with your favourite blade, the blade itself loses its magic. It's like eating everyday your favourite dish. How can it remain your favourite if you eat only that every day?!