The argument is roughly that it is, in fact, not very useful, while opening up a vast array of misuses - especially in the domain of being all too clever. What does "+" mean on a list and an object? Add, probably. But what if it's two lists? Union? Or add the second list as the last element to the first? Named functions "add" and "union" aren't any less readable and loads more descriptive.

The only situation you positively need operator overloading is when doing arithmetic, and you should do that using the built in types. This, of course, sucks when the built in types are inadequate, and you e.g. want to use a arbitrary precision library such as BigDecimal in Java.

This, of course, is an opinion, and I'm not shy to admit it's been shaped by being burned by Lift, the Scala web framework which makes heavy use of symbolic function names which makes it incredibly difficult to talk about or search for answers online.