Um... how many ORMs do you have experience with? I suggest you look at the mentioned sqlalchemy core's ability to map more or less directly to SQL with reduced syntactic ugliness.
There is a fruitful discussion that can be had on helpful ORMs vs harmful ORMs, and it usually ends up describing a category of marshalling helpers that don't quite form a regular ORM as the ideal situation.
My take-home on the whole thing is, you need something that makes working with relations in your code easy but you don't need something attempting a ridiculous abstraction like "relations are objects."
