Clemens Vasters has posted an interesting article about O/R mapping.  I can admit that I am one of those people who is drawn to the beauty of an O/R abstraction, and have been since first experimenting with Jasmine and PostgreSQL years ago, and the ideas are obviously much older than that.

After exploring my own O/R implementation I must admit that there are problems with the "aesthetics of the abstraction" as well.  You are seldom working with a fully populated domain model, and lazy loading and the like carries with it its own trade offs.  I'm a bigger fan of Code Generation than pure OR mapping these days.  At any rate, read the article if you are interested in O/R mapping