Here's the SB I'm playing right now:

// Sideboard
SB: 1 [US] Ill-Gotten Gains
SB: 1 [SC] Tendrils of Agony
SB: 2 [US] Duress
SB: 1 [6E] Diminishing Returns
SB: 1 [TSP] Empty the Warrens
SB: 3 [GP] Shattering Spree
SB: 3 [IA] Pyroblast
SB: 1 [TSP] Grapeshot
SB: 2 [SC] Xantid Swarm

My SB strategy is usually this:

Non Blue decks:
+2 Duress -2 Chant
Non Blue decks with artifact hate:
+2 Duress +2 Shattering Spree -4 Chant
Blue decks:
-2 Cabal Ritual -X Ponder -1 Chain of Vapor +2 Xantid Swarm +2 Duress +X Pyroblast

So after SB I got a package of 4 Chant, 4 Duress, 2 Swarm, 3 Pyroblasts against blue decks.

Swarm has some advantages compared to Shusher:
- Costs 1 mana and zero to activate (no mana in your combo turn)
- Not needleable
- Not blastable

I believe Swarm is overall better against Counterspells/stifles/chants, and generally in fast games, where shusher is better against CB and long games.

Once CB lands you have some possibilities:
- Have Shusher (a 2of) and Pyroblast (a 3of)
- Play Pyroblast and hope the opponent doesn't have 1CC on top.
- Play bounce (Xcc) and hope the opponent doesn't have X on top.

So I take my chance and just hope to deal with CB before it comes into play. I have some chances to do it.
- I can combo before turn 2.
- I can play a turn 1 Swarm and win protected on turn 2 on the play
- I can discard it with 4 Duress
- I can counter it with 3 Blasts

I believe that this configuration actually gives a better Counter matchup, while still being solid against CB.
Duress is also much better than chant against everything non-blue.

What do you guys think?