A year ago, I was very skeptical of Ruby 1.9. There were a lot of changes in it, and it seemed like it was going to be a mammoth job to get things running on it. The benefits did not seem to outweigh the costs of switching, especially since Ruby 1.9 was not yet adequately stable to justify the big switch.
At this point, however, it seems as though Ruby 1.9 has stabilized (with 1.9.2 on the horizon), and there are some benefits that seem to obviously justify a switch (such as fast, integrated I18n, better performance in general, blocks that can have default arguments and take blocks, etc.).
Perhaps more importantly though, Ruby's language implementors have shifted their focus to Ruby 1.9. It has become increasingly difficult to get enhancements in Ruby 1.8, because it is no longer trunk Ruby. Getting community momentum behind Ruby 1.9 would enable us to make productive suggestions to Matz and the other language implementors. Instead, we seem to get a new monthly patch fixing Ruby 1.8.
So my question is: what do we as a community need to shift momentum to 1.9. I'm don't want a generic answer, like "we need to feel good about it". I'm asking you what is stopping you today from using Ruby 1.9 for your next project. Is there a library that doesn't work? Is there a new language feature that causes so much disruption to your existing programming patterns to make a switch untenable?
I suspect that we are all just comfortable in Ruby 1.8, but would actually be mostly fine upgrading to Ruby 1.9. I also suspect that there are small issues I'm not personally aware of, but which have blocked some of you from upgrading. Rails 2.3 and 3.0 (edge) work fine on Ruby 1.9, and I'd like to see what we can do to make Ruby 1.9 a good recommended option for new projects.