In general this is true, but with Rails 4, we added a lot of Postgres specific features to ActiveRecord, so you can actually take advantage of all the awesomeness Postgres has to offer.
When I first got to Rails it seemed that databases were considered as a bothersome but unavoidable necessity; flat files with a funny accent, instead of an essential and powerful ally in the fight against entropy and error.
In the past several years Postgres and NoSQL data stores have gained in popularity and become mainstream, and Rails now supports them well. The Rails ecosystem historically focused on MySQL, but that's not the case anymore. For example, Engine Yard now uses Postgres by default, and Heroku always has.
That looks mostly like you've added support for postgres "extras", not (inherent) "postgres goodness". Not that adding support for "extras" is a bad thing -- but in the context of "adding support for postgres sql" -- that seems somewhat orthogonal? (I'm not saying it is wrong for rails to approach postgres this way, just that the approach doesn't seem to change the way rails (afaik) approach databases: logic should be in rails, not in stored procedures and views (which is where it would make sense to place logic, if you design with "database first")).
Yes, that's true. The approach has it's drawbacks though (validates_uniqueness_of being a prime example).
As much as I like Rails, I sometimes wish it were designed with the database playing more of a role than just dumb storage. Defining things like validations in Ruby is certainly nice and easy, but the database is much better suited to actually enforcing such constraints.
Check out this blog post: http://blog.remarkablelabs.com/2012/12/a-love-affair-with-po...