I'm a C# developer who learnt objective-C and started down that path, went to Monotouch when it came out as it made sense. I trust people who specialise in memory-management to do a better job at object allocation and deferencing than I can do manually.
I'm annoyed that Monotouch and a few others are essentially caught in the cross fire of what is clearly an Adobe hate campaign. Monotouch makes you write using wrappers around UIKit and doesn't water down Cocoa unlike the Flash libraries do.
I would love to see a solution where the clause was slightly amended to read "C-derived language" (though arguably ECMAscript is based on C). They would also need to remove the tools clause which won't happen. There has to be a court case over this if it doesn't change, and I fear Apple will probably win.
Monotouch has been out since November 2009, Adobe CS5 isn't out for the iPhone yet, and as for Titanium I don't know the exact time period but it's not been long.
The only platform producing apps for a longer period of time has been Unity3D, which now advertises itself as having over 600 appstore games.
So your argument about raising the barrier to entry is weak, as these tools have only just emerged in the last 6 months. Prior to that we've seen thousands of poorly written, leaking objective-C applications on the AppStore. I've seen 2 RSS readers and the official digg.com app crash straight to springboard in the last 2 weeks, all written in objective-C.
Just because the language is closer to C and enforces memory management doesn't make its barrier any higher or require any greater skills - it means you'll get a tonne of apps that aren't releasing or reference counting and crash. I'm sure all this was hotly debated 10 years ago and garbage collection won.