Interesting. Could you point me to some resources that details best practices with regards to developing and deploying JRuby apps? I will definitely take this into consideration whenever a new project rolls along.
Some confuse the speed differences. Generally, any work station that has dual or multi-cores will see an increase in speed once the initial set-up time has competed. remember all Virtual Machines have a set up or initialization time period.
I've tried JRuby (I think it came with Netbeans) and one thing I noticed is that it's slower than native Ruby. Still, having access to the Java platform from your Ruby apps is a pretty slick and useful feature.
But there are alternative jruby gems for things like mongrel or openssl. Works fine, though I don't know of a drop in rmagick replacement right now.
Well, JRuby is probably the best alternative implementation of ruby programming language out there. It also implements rubygems library manager.
One thing that you have to keep in mind that some of gems, that for example use native ruby extensions (C, C++ code etc) won't install. On the other hand you'll get access to all the Java stuff, and some extra gems too.
JRuby is also faster on Windows.
Yes, it supports rails. Why don't you try out yourself creating a demo application? There are still several gems which need to be released into jruby version. But still, (j)ROR works, I myself have created a sample application on it.