@ravager101 I am aware of all of those issues and they don't seem like particularly amazing arguments to me.
I can see the argument that Serenity is "slow" in that your opponent knows it's coming, of course, and you are correct in that it blows up your own artifact mana.
But as you mentioned, people are playing Ancient Grudge and By Force. I can see Grudge being better in a way, since the 2-for-1 can be distributed over multiple turns, but then you're getting hit by sphere effects twice over, so it has its downsides. I don't think Serenity is any slower than By Force against a deck that dumps its hand on the table in the first 2 turns. On a side note, I am not sure I'd agree that Ancient Grudge or By Force can be considered "effective hate", but that is an entirely different discussion.
Also, I wasn't suggesting that you could only rely on Serenity. There are scenarios where Ravager + Factory still kills you, but only about 20% of keepable hands are going to contain that combination. And about 20% of the time, you'd have Swords + Serenity (assuming you're playing 4 of each) as a solution.
I also don't agree with your comparisons to Hurkyl's. Being able to replay all the cards is significantly different than destroying them when you're not combo-ing out. The lower-to-the-ground variants of Shops will, in many cases, have played most of their hand when you cast Serenity.
Aside from "I'm not playing white", this isn't making sense to me. There was a whole year where nearly every blue deck was in white for Mentor and we still didn't see anything in sideboards except for 1-for-1 artifact removal (with a few exceptions).
Have you (or anyone that you know) actually tested this card in the matchup with a significantly large sample? I am happy to be wrong about this, but anecdotal evidence is all I've seen.