He's OP against people who don't have experience against him and low elo, but also OP against Sona lanes, Soraka lanes, Ashe lanes, Teemo lanes, and Kog lanes. Watch out for other kill lanes (or Alistar in general), since they have basically the same goal as you, but with less cooldowns. Once you get a feel for how far the grab goes, learn to smartcast it if you don't already, because you will miss so many opportunities if you hesitate. Seeing the arrow will make you think twice about the grab whether you want to or not.
edit: also try not to pick Blitz to pair with Ashe or Kog. They can work but it's just not as effective and more risky. Blitz/Teemo works well enough though. Tell your AD to just follow through with you if you make a grab - if you're not on the same page then everything will fall apart.
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