The first release candidate for Ruby 1.9.2 is due end of May and I believe many are waiting for 1.9.2 to hop on the 1.9 train.
Not really an answer to your question, but to start writing code uses 1.9.2 methods now, you can require "backports" and most features will be available to you, even in Ruby 1.8.6 (albeit not nearly as fast, of course).
