I personally don't really feel the effects of stage 1 slow when it is used against me, or when I am using it on opponent. The effect of it is so small it is not that noticeable. I remember using Nobel and tossing it on the opponent, but still can't catch up to them. But I guess Vandol is right in that for Sword Calamity's case, it's effect is multiplied by the fact that Sword Calamity has a naturally high speed.
Even though I don't have the luck to own 1 yet, I've tried it out on Shift's account, and good lord it's swings and cancels are legendary, even for a rock noob like me. Cancels easily either on the first swing or the second swing. It's huge swing arcs and the axes it covers make air catching really easy.
What I dislike about most Sword Cala players is that they finish connecting the W3 blow and KD the opponent, making the boost down less effective imo. The same can be said for most Sword Strike/Epyon/Nataku players. It would be a lot better for the team if the opponent is kept boosted down so that we can shoot and kill fast to remove them from the field.