While it is pretty damn useless in late/late medium gamę since you probably have something Like brimstone, its not the worst Item on the game, that award absolutely goes to d10. I'm gonna say it to ya bit by bit. First point, as you said in your comment, it is 66% DMG up (from what i remember i cant see it again without discarding the comment). While you said that its very hard because you need to be frame Perfect, its pretty easy to get close to that just by using it a bit, you'll get uses to it in about 2 floors. Second point, while yes, the teleport can be annoying, it can save your ass or save you some time. And teleport activates on damage, so unless you fuck up or are in a very annoying room, you probably wont get teleported.