One topic was the long road to full regular expression support in JRuby, which finally ended in a port of the Ruby Oniguruma regular expression library to Java.
The interview also contains Ola's views of the future of Ruby, and in particular JRuby. JRuby is mentioned as having advantages since benchmarks show JRuby to have a speed advantage over MRI for some areas. JRuby also serves as a way to get Ruby into enterprises that don't consider Ruby yet - Ola recites an anecdote how this was achieved without much fuss.
Watch the "Ola Bini Discusses JRuby" interview.