Interesting, For many years I was all in on MRI and down on JRuby but over recent years I've been quite happy with JRuby for certain things.
The reality of JRuby startup times make it not a good fit for scripting tasks but otherwise server and threaded tasks are a great fit. Since using JRuby more recently I feel the ecosystem support is probably the best of the non-MRIs. I rarely run into compatibility issues. Conversely JRuby's Java integration has been a very useful feature that no other Ruby implementation offers.
The reality of JRuby startup times make it not a good fit for scripting tasks but otherwise server and threaded tasks are a great fit. Since using JRuby more recently I feel the ecosystem support is probably the best of the non-MRIs. I rarely run into compatibility issues. Conversely JRuby's Java integration has been a very useful feature that no other Ruby implementation offers.