More info on Cocotron can be found at http://www.cocotron.org/. Their stated goal is:
The purpose of the project is to provide an easy to use cross-platform solution for Objective-C development.
There’s a blog post at Mac Daddy World at http://macdaddyworld.com/2008/10/27/adventures-in-cocotron/
Now I can say with some certainty that xCode and Objective C isn’t as easy to learn and use as REALbasic but a programming language is a programming language and we can all learn “one more” language and IDE. Certainly one of the truths about REALbasic is that all of it’s controls are a compromise and not as feature rich as their .NET and Cocoa brethren. Cocoatron has the potential of changing some minds of people who might be looking at REALbasic and go with Cocoa if controls on both platforms are nearly identical.
It seems that Cocotron isn’t an officially supported Apple product but that might not matter in the long run if enough developers start using it. Stranger things have happened in other platforms where something becomes a de-facto standard. It wouldn’t surprise me either that Apple has a skunkworks project that does this as well so it’s possible that at any point Apple could go, “Because of demand, here’s the official Cocoa for Windows frameworks.”
One major issue I see with Cocotron is that you can only do code development on the Mac. That is certainly one of RB’s strengths where you can run on Windows, Linux or Macintosh OS X and compile and debug for the other platforms (Pro editions only).
One thing that is similar to RB is that it looks like you can debug your Windows app while running in the xCode IDE. I wonder how fast or slow that is? I might just fire up xCode this weekend.