It's hard to imagine using an ORM for anything high volume that just got around to adding (still very limited) connection pooling. I'd tend to think anyone overly concerned with performance would use SQLAlchemy, if they use any ORM at all.
right tool for the job. Djangoś ORM is great for simple stuff. And it works with the admin interface (which is worth a lot). If You need something complex enough, use raw SQL.
The admin was too much to give up to swap the ORM to SQLAlchemy for me.