Just go to the release announcement and major features blog post by DHH already!
If you're having trouble installing the Rails 2.0.1 gem, do a
gem install rails -y --source http://gems.rubyonrails.org
Now that the obligatory link to the Rails 2.0 release announcement is done, I'd like to urge anyone with any interest in improving Rails or seeing new features or fixes in Rails to try and contribute to Rails. I'm sure everyone of us Rails users have had "what if Rails could do this" or "why is Rails doing this, that's just wrong" moments. Well, roll up your sleeves and help by contributing instead of complaining about how "they" won't/haven't/are too stupid to fix it..
A good starting point is to read the Rails Trac wiki, and after that be sure to check out John Susser's excellent guide to contributing to Rails (read the presentation slides, it won't take long). You should have enough information to start. I recommend just opening the
base.rb classes for ActiveRecord, ActionController and peeking around the ActiveSupport classes just to get a feel of things. After that crack open the relevant test for your issue and write your test-driven patch!
It's really easy, since Rails is written purely in Ruby - if I can do it I'm sure you can too :) Your contribution doesn't even have to be a bona fide patch file with tests, documentation and bits of Ruby code - if you notice a bug and report it not knowing how to fix it, that's good enough! Or even something as trivial as a new style (CSS and layout) for the Rails error pages (there isn't such a patch yet but I'd love to see prettier default exception pages instead of the current rather plain-looking ones).
Anyway, that's enough of the sermon from me - enjoy your Rails 2.0! Congrats to the Rails Core team and contributors on another solid release!