It can be installed via rubygems:
"gem install mongo"
"gem install bson_ext" (for the optional extensions)
Or updated via "gem update mongodb"
Please see the release notes here:
http://api.mongodb.org/ruby/1.6.2/file.HISTORY.html
Highlights:
* Implements socket timeouts via non-blocking IO instead of Timeout module which should greately increase performance in highly threaded applications
* Added ability to authentication via secondary if primary node unavailable
* Replica set refresh interval now enforces a lower bound of 60 seconds
* Added documentation for dropping indexes, collections, databases
* Test output cleanup (...)s unless failure occurs
As always, please report issues on Jira.
-Tyler