I would just go for objective-c. MacRuby is in version 0.1 and might be more of a headache to figure out and circumvent bugs and holes then just learning objective-c. It's not a very difficult language and easy enough if you have tried C or Java before. You'll also need to handle memory (allocation and deallocation), but you could try to rely on GC, but not for iOS. Lynda.com has a video tutorial on objective-c and also tutorials on iOS programming.

MacRuby was version 0.1 about 3 years ago. A lot happened since, and we expect the next release to be our 1.0 RC. For Cocoa development, it's very stable, we haven't received any critical bug report since at least 3 releases.

Ah. I read 0.10 and thought 0.1. It's a logical mistake to make since 0.1 is a number and is the same as 0.10, I know a lot of other people count releases the same way, but skipping 0.10 might be a bit helpful, or keeping to a strict 0-9 policy. I saw Linus got tired of the 2.6.39 counting and just skipped ahead to 3.0.