I've used ORM tools such as the one in Django, Active::Record and DBIx::Class.

I do not have the issues you mentioned ... I always remember the API calls I need to make and performance has not been an issue (granted, I'm fairly familiar with all issues that can come up, so I know when or where to optimize in general).

    the ORM usually pulls in the full object model for each student

Here's how to do it in Django (and note this is off the top of my head):

    for row in Student.objects.values_list("gpa"):
        print row[0]

You're really talking about shitty ORMs or APIs you haven't had the patience to become familiar with.

    by the time you figure out the right
    incantation you may as well have written the 
    SQL yourself

That's not true. On complex filtering, you often want to add or subtract filters based on certain conditions. With plain SQL you end up doing really ugly string concatenations, whereas with a good ORM the queries are composable.