I'm becoming increasingly convinced that there is only one good ORM and the rest are fit only for CRUD operations. ActiveRecord. The abstraction it provides is amazingly flexible. You can be as close to the SQL as you want to be.

With other ORMs, any time I need something not CRUD, I wind up hand-generating SQL. With ActiveRecord, I never need to. Looking at generated SQL, I do all the time with AR, happily it makes that very easy for me. Including my own SQL snippets in scopes? Easy. Hand-generating joins? Almost never.