There was a talk by Yehuda Katz where he predicted that most plugins that modify the router in Rails 2.3 will either be unnecessary in Rails 3 or reduced from 200 lines to 2.<p>With what I've seen so far this seems to be absolutely the case and shows how much one can gain from switching to a clean architecture.
It's really great Rack is used so heavily in the router, it really makes Rails more modular, and demonstrates the value of Rack.<p>I'm looking forward to some of the same ideas being applied to server-side JavaScript / JSGI.
I have been occasionally building Rails 3 and trying it - can't wait to switch work projects (probably do this a month after official release). There is obviously a lot of talent on the rails dev team and it shows with the willingness to keep improving the architecture.