We're just getting started with DataMapper too. Lots of things planned in the future as we refine the API and internals.
For example, we're looking towards allowing normal ruby objects to be persisted, not just objects that include DataMapper::Resource. I'm also working on a query/adapter layer that will allow more complex queries to be constructed similar to ARel called Veritas (http://github.com/dkubb/veritas/), except it will include alot of the things we've learned about working with 40+ datastores, some vastly different from RDBMS.
Dan -- thanks for all your hard work! I switched to DataMapper last October and haven't looked back.
For those who aren't aware, DM is like ActiveRecord if it had been designed by a seasoned Ruby programmer who also lives and breathes relational algebra. The method chaining is so powerful you will find yourself amazed that it works, then extremely impressed when you see the SQL that was generated.
I've heard of a few things on the roadmap and they are awesome. Now that DM has gone 1.0 (stable API) I can see no reason why anyone would use AR for a new project.
For example, we're looking towards allowing normal ruby objects to be persisted, not just objects that include DataMapper::Resource. I'm also working on a query/adapter layer that will allow more complex queries to be constructed similar to ARel called Veritas (http://github.com/dkubb/veritas/), except it will include alot of the things we've learned about working with 40+ datastores, some vastly different from RDBMS.