There are other issues with the MERGE statement. It has bugs… some of which can cause database corruption.
Here we have a Shiny New Toy (feature), supposed to make life easier, yet it causes problems. Until it can perform better (and the bugs are eliminated), I just don’t use it.
Beware the Shiny New Toys.
Wayne makes a great point. Not all new things are good, even when they’re potentially quite useful. I love shiny new toys a lot, but part of being a database administrator is protecting data, and part of that means being able to trust your tools. Sometimes the tools work really well right out of the gate, and sometimes (like in the case of MERGE) they don’t.