With the release of the half-baked 1.8.7 a few months back, and now 1.9.1 being called the "first stable version of the 1.9 series" I'm a little bit confused as to what "stable" means for Ruby now.

Is 1.9 still going to be considered a development series, not widely recommended for most apps until 2.0 is released? Or is that starting to gradually change?

The plan has been for 1.9 to be a stable series for a long (at least over a year) time now. I'm not sure there are any concrete plans for 2.0 at this time. If you use Ruby, now would be a good time to start getting comfortable with 1.9, though there doesn't seem to be much rush.

I updated one of my projects to work with 1.8.6 and 1.9 a couple months ago and it was mostly painless. I'm looking forward to the nice performance improvement and some of the api changes when it becomes production ready.

ruby 1.9.1 is mainly stability fixes to ruby 1.9, which had a few .. quirks.

for a less-than-complete guide to ruby 1.9 features, consider reading eigenclass's summary from way back: http://eigenclass.org/hiki.rb?Changes+in+Ruby+1.9

"... consider reading eigenclass's summary ..."

"Last major update on 2007-10-12"

Casual lurking on ruby-core suggests that all sorts of things have changed since then.

It's still a fairly decent reference if you need to update your software for 1.9. Several incompatibilities I ran into were listed there. For others problems, I did have to search the mailing lists, though.