There is a lot of hearsay in this post from developers that have not tried MonoTouch and Objective-C. It seems to be mostly be Objective-C developers that have never tried MonoTouch.
I am obviously biased, but you can check out what the MonoTouch community has been up to in:
http://xamarin.com
There you will find several articles from developers that have developed in both Objective-C and C#.
