Excellent point. However, dropping into another language does have all sorts of disadvantages: apart from the learning issues, there's the lack of compile-time syntax checking and type checking, the cost of dynamic compilation/interpretation, etc.
One thing to look at, perhaps, is how it translates into Scala, where you can define your own operators:
A.flatMap(B) --> A/B
A.attribute(B) --> A @ B
etc; and then we start to have something very XPath-like, but with a syntax that's compiled and validated by the host language.