Not that I've found... I've got a fairly large database schema, partially defined in ruby, partially defined as actual PostgreSQL statements, with referential integrity, triggers, views, etc, and ruby's coping with it fine.
For some reason to make a model that queried a view in the database, I had to add this to the model definition:
def self.inheritance_column
"none"
end
I can't remember if that was due to the table actually being a view, or if there was some other reason for that... but Ruby and PostgresSQL have been playing together very nicely for me, even with a heavily customized/programmed DB on the PG side.
Cheers, Tyler