As I was working deep in Scripturian on Lua, I thought I might as
well give Nashorn a try. Nashorn, to remind you, is the JavaScript
engine which will be bundled with JVM 8.
The bottom line is that it works, and I don't foresee any problems
moving from Rhino to Nashorn in the future. It's hard to say
anything much about performance without serious testing, but I'll
believe the claims that it can be several times faster than Rhino.
I you want to give Nashorn a try, but are wary of trying the entire
JVM 8, there's actually a moderately-well maintained backport of
Nashorn to JVM 7:
https://bitbucket.org/ramonza/nashorn-backport