I'm a Ruby developer, not iPhone/Cocoa so this could be way off base, but I believe this is what it came down to in a previous discussion.
Here are the highlights from the latest Status Report from 0.5, posted by Laurent on Monday at http://lists.macosforge.org/pipermail/macruby-devel/2009-Nov...
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Enjoy! The final 0.5 release is not far at this point :-)
Highlights:
- rdoc, ri, rack, sinatra are now working.
- DTrace probes are available. Same as in MacRuby 0.4.
- BigDecimal, OpenSSL and JSON support (experimental).
- macrubyc: support for building fat binaries (using the --arch argument).
- New tool: macruby_deploy, to help you deploying a MacRuby application, by ahead-of-time compiling its source code and relocating the MacRuby framework inside the application bundle. One-click Xcode targets provided.
- Lots of bugs fixed, especially related to compatibility, thread-safeness and memory/resource leaks.
If I had to write a Mac app, MacRuby and HotCocoa look great.