[compay]

I think the main reason is simply that 1.8.6 has been "good enough" for most people. It reminds me a lot of Apache 1.3 vs. Apache 2.0.

For a long while, there were also no debuggers for 1.9.1, which is a big deal for some people. Mark Moseley has done a lot of work to get them working on 1.9.1 so luckily this isn't really a concern any more.

http://github.com/mark-moseley

I made Ruby 1.9 my default Ruby using Macports (using the +nosuffix variant) a few months ago. Other than finding a few trivial bugs in my code and some other people's, it's been painless; though of course your mileage may vary.