And with GC on the way out in OS X... MacRuby has their work cut out for them.

GC is on the way out? I haven't heard that before... have a link?

End of the page here: https://developer.apple.com/library/ios/#releasenotes/Object...

Apple highly encourages using ARC over GC for new development.

Well yeah. One is compiler-assisted reference counting and the other is garbage collection. Reference counting is nearly always faster than garbage collecting, and Apple has generally been a bit obsessed on speed, for however much that has gained them or lost them.

Their wording there is suspect though. Interesting - thanks for the link!

Reference counting is generally quite a bit slower overall than stop-the-world garbage collection.

I guess you meant latency, where reference counting generally has better latency than incremental garbage collection.