Doesn't look like they've put together an official changelog yet, but the major changes off the top of my head would be jQuery, Coffeescript, sass, sprockets, css sprites, flushing & deprecation of rails 2 finders.

A few niceties:

1. Console shows SQL queries right there.

2. The file_field automatically adds :multipart => true to the enclosing form.

3. Newer Migrations - There is a "change" method now which can be used to write only the "up" part of the migration and Rails will automatically reverse when a migration is rolled back.

IMO the most important improvement is the IdentityMap

I'm very much looking forward to making use of the associations rewrite by Jon Leighton (http://jonathanleighton.com/).

Nested has-many:through relationships are a go! :)

Care to explain? I haven't hear about it.

http://edgerails.info/articles/what-s-new-in-edge-rails/2011... is a good synopsis of IdentityMap.

The IdentityMap makes sure that there is only 1 ActiveRecord instance for a given row in the database.

This basically means that calling Article.find(3) and Comment.where(:article_id => 3).first.article both return the same instance.

Oh, it is in finally? Exciting!

I've gathered up the changelog entries into a gist: https://gist.github.com/958283

I just started learning rails...and I love it.

I am not an excellent hacker but I am learning more by the day. Ruby + Rails is very fun.

Rails is the new PHP, sigh.

Mountable engines seems to be major to me. I think (or hope) it will ignite a whole new slew of cool gems.

Definitely looking forward to HTTP streaming and the new SASS/JS asset handling!

anyone know how the flushing/template streaming works? Is it automatic or do I need to turn it on? How does it know when the head ends?