I've decided to use an upcoming sabbatical to teach myself OS X and iOS programming. My background includes OS X systems administration and web development, mostly using the Apache/MySQL/PHP model. I'm familiar with OOP concepts and have trifled with any number of languages from C to AppleScript, but am not fluent in any object oriented language. I've been exploring Xcode 4 for a week and feel conversant with the IDE if not yet able to accomplish anything with it.

So… I understand that Cocoa is a given, but today's million dollar question is Objective-C or MacRuby? I'm a blank slate with regard to both and so could use some good advice. For example…

What are the advantages of MacRuby over Objective-C?
What are the advantage of O-C over Ruby?
Is Xcode's support for O-C significantly better than it's handling of Ruby? Do I care?
At this point I'm primarily interested in OS X development, but iOS clearly needs to run a close second. What's the current status of Ruby development for iOS and is it likely to go anywhere in the nearish future?
Any thoughts on the longer-term prospects of either language?

Any thoughts from anybody will be much appreciated.

Thanks,

Bryan