Jeez, remind ==Me== never to put forth an opinion again. It's like walking into the lion's den.
Screamers cost as much as a Bloodletter and have no use against armies like Orks or Tyranids. It's a small unit, easy to kill, and extremely specialized. I think Flesh Hounds and Seekers take up Fast Attack slots better; they may not have the same role but you only have so many Fast Attack slots. If I had points to spare I'd take a few, but I'd rather just throw a bolt or two onto a unit of Horrors, use the Big Bird, or just hit it in combat with a MC.
But hey, that's why we have the thread. To discuss this sort of thing. I'm not a big fan of Screamers, but obviously other people are. I'd say that's a good indicator of internal balance for this Codex.
Keep it up, there's plenty more to bash ==Me== over