Version 0.9.5 fixes the broken rebundling from 0.9.4, and each instance now generates new SSH keys on first startup.
Major changes in the last few versions:
* Multiple instance support
* Support for new instance types (i386 and x86_64 versions)
* Ubuntu 7.10 "Gutsy"
* Capistrano tasks available as a rubygem
For details see the project web site:
http://ec2onrails.rubyforge.org/btw, it takes a while before new gems are available after they're uploaded to rubyforge, so it might be another hour or two before "gem update" will give you the newest version of the gem.
Paul