When Rails 1.1 came out we didn’t want to break our existing apps (not that we were doing anything that would have broke, but why take that risk) so we did the prudent thing and “froze” our apps with the gems for Rails 1.0. That Rails allows you to do this is such a stupid-easy way isn’t that surprising. What’s also nice is that once you’ve tested on Rails 1.1 it’s just as easy to undo, rake unfreeze_rails.
That’s it. Did you expect more?