I tried out skarner the last time he was free and loved him. I starting saving my IP for him, but since then he has been nerfed. I wondered how much the nerf has affected him and whether he'll still be a wise 6300 spending.
Basically his shield is no longer up ALL the time in teamfights. Only most of it.
You also have to be a bit smarter with how you use it while getting around. Since the cooldown is much longer you can't just randomly use it and know it'll be back up by the time you get there. A few auto-attacks solves that too though.
Now these points of data make a beautiful line, and we're out of beta we're releasing on time! So I'm glad I got burned, think of all the things we learned!