Hmmm Cocoa Touch much nicer than .Net?
I'm building iPhone apps at the moment and although i like Objective-C, I'm finding alot of things lacking in the Cocoa Framework such as decent XML support and WS* web service support for examples.
I do like interface builder though and using proper design patterns such as MVC built into Xcode templates, but I think saying Cocoa Touch is better than .Net is a pretty blinkered view or at best an opinion.
And as for learning Objective-C it really isn't that hard if your already an OO developer, in fact it's a pretty simple language. The hardest part is reading through the documentation and getting to know the Cocoa framework libraries. Apple provide very good documentation for this IMO which is all easily downloadable as PDF's
Your going to have to learn the UI framework and design patterns whether your using native Cocoa or Mono, yeah it would be nice to maybe use C# and a first class language against different frameworks i.e. Cocoa Touch but that a nirvana that's not gonna happen.