I have used Rails on a daily basis for almost a year now, and before that I was a night time hangaround. While I am definitely a happier programmer using Rails than anything built on Java, I still feel that it can get better.
First of all I want more things to be plugins. And really, they should not be plugins at all but gems instead.
Why plugins? We use RSpec instead of Test/Unit, HAML instead of erb and are seriously looking into JQuery instead of Prototype. And of course, we are using Mercurial instead of Subversion. All of this is of course possible to use in Rails, but a lot of things are sort of made for the default choice, such as generators generating tests, and plugins having the -x switch for Subversion. And I am pretty sure that this is the way DHH wants it.
So, when 2.0 is now released, I see that the Rails community as a whole does not see the same problems as I do. If they did, they would have done more like the stuff above, instead of sexy migrations and ActiveResource.
This is where Merb becomes really interesting. I have looked at it before not understanding its value, but now I see a framework that does everything I want Rails to do. Gems as plugins and very agnostic about templating languages, Javascript frameworks and even ORM frameworks - almost a heresy in Rails. I will definitely think about using it instead of Rails in the future.