A few years old, still a good read.
At ﬁrst, the Objective-C language seems to be an obstacle rather than a boost for Cocoa programming : it was so diﬀerent that I couldn’t get into it. It took me some time to appreciate its challenges, and understand the many helpful concepts it supplies.
According to me, C# is, despite a bunch of advanced concepts, far less interesting than Objective-C, because it gives hard access to simple Objective-C features, and the Cocoa API quality is miles ahead of .NET. This personal opinion is not the subject of the present document.