Sigh. There is so much misinformation being spread by today's software engineers without proper CS backgrounds. As anybody who's read Date and friends knows, relational databases are fundamentally more expressive (and therefore better) than network databases (which is the model used by object databases), being grounded in set theory and predicate calculus.
Your bad taste for relational databases is more likely a result of using a crappy ORM pattern (such as Active Record). Go try a proper implementation of Data Mapper (I can't recommend SQLAlchemy highly enough), then come back and tell me how you feel.
That sounds dangerously like pedantry to me. The point is not that the mathematical expressiveness of the network model is as powerful or more powerful than what you can do with relational stuff. The point is that the network model maps nearly 1:1 with the actual programming model used to implement the application logic.
All that relational goodness does you no good if you want to architect your application using an OO data model in a web application server. Maybe you're trying to argue that that's the wrong way to do web applications? But if you accept that people want to use Rails/Django/etc... then you have to also admit the argument that RDBMS's are the wrong tool for the job. This is true for the same reason that a Dremel is the wrong tool for framing a house, despite the greater expressive power of the Dremel's cutting tools.
I'd actually argue the best approach is to develop both sides fully: I agree that an OO data model is the best fit for non-trivial application logic, but I also believe relational databases make the best data stores. The two can coexist just fine, it's just a matter of selecting the proper design patterns and supporting libraries -- which is why I mentioned SQLAlchemy. In its developer's words:
"SQL databases behave less like object collections the more size and performance start to matter; object collections behave less like tables and rows the more abstraction starts to matter."
This false dichotomy that's always presented is distracting, and leads to people naively taking religious positions about what should in fact be a non-issue.
Would you argue that the ability to form ad hoc queries for answering questions not originally imagined when writing an application fails to make the relational model superior to something without that property?
(I see you develop with Rails though, so probably yes.)
Your bad taste for relational databases is more likely a result of using a crappy ORM pattern (such as Active Record). Go try a proper implementation of Data Mapper (I can't recommend SQLAlchemy highly enough), then come back and tell me how you feel.