I have 300 Derby Extra and 300 Derby Premium. They are like the opposite extremes. The Derby Extra are the dullest blade i 've seen. 1st shave, with much work, i can get BBS. 2nd shave, i get areas of BBS with areas of DFS or worse. I usually toss it at the 2nd shave. But extremely smooth blade (because it's not sharp).
Derby Premium is completely different animale. The edge still feels "derbesque" (due to the coating being the same), but it's much sharper and considerably less smooth. Although i think i 've used only 1 or 2 blades till now. I mean, you must be careful with this one, it's nowhere near as dumbproof as the Extra. And also the edge lasts longer (i think i have gone to 4 shaves). I don't like non smooth blades much, but i am a sucker for nice packaging and this is why i bought 300 of them. But, i wouldn't reccommend anyone to make a blind purchase of 100 before trying a tuck, based on what they know from the Derby Extra.