Over the past months I've been refactoring ActiveSupport::Multibyte and made it run on Ruby 1.8.7 and 1.9. If anyone is interested in a write-up about the API changes, please let me know.
I've posted the changes as a patch to ticket #951:
http://rails.lighthouseapp.com/projects/8994/tickets/951-multibyte-revisited
You can also pull the changes directly from the multibyte-revisited branch:
http://github.com/Manfred/rails/tree/multibyte-revisited
Manfred
p.s. I hope you're not getting this multiple times. It seems Google Groups is acting up.