Mmm. I don't know if you guys can handle this much excitement on a Friday, if not, come back tomorrow for a recipe or something.
People ask me a lot about putting dropouts with a replaceable derailleur hanger on their bikes. I usually tell them something snide about how I wouldn't know, since I *only* ride rigid 29" singlespeeds with bullhorns and a pink chain to match my ironic 80's style American Apparel t-shirt. They're usually so humbled by my glory that they just give up at that point, but today I'm feeling generous, so here we go.
My feeling is this: I've built hundreds of steel frames, and I've had zero (nada, zip, zilch) come back for hanger repairs. Those hangers are burly - 1/4" plate steel doesn't bend easily. You'll shred that derailleur long before you do much to the hanger. And they're really easy to bend back with a $25 tool (Park DAG-1) if you do manage to bend them.
Replaceable hangers are a great idea for aluminum bikes, where the hanger is A) weaker to begin with, and B) can't be cut off and re-welded without spending a fortune re-heat treating the frame. But I don't build aluminum bikes, eh? I'm happy to do a replaceable hanger dropout (Paragon makes a nice one that I normally use when my logic-dropping fails to sway someone), but in my experience, they break all the time and have to be constantly replaced. Given that the replacement hangers are $15 or so, it's not a great investment IMO. Sure, you can carry a spare hanger around in your pack, which you can't do with a non-replaceable one, but honestly, it's not that hard to ghetto-singlespeedify your bike to get home anyway if you really need to.