"return" from method while stepping?

Unfortunately in Xcode 4.5.x there is no way to force an early return from a function. In the current lldb sources over at http://lldb.llvm.org/ there is a newly added command, thread return, which does what you want - it includes the ability to specify the return value of the function. This won't be in Xcode until the next major release, though.

When you are debugging using Xcode and when your program is paused at a breakpoint, you can drag the little green arrow to any other line in the function. E.g. in the following code:

if I want to skip the NSLog(@"B"), I can simply drag the green arrow from line 20 to line 23, which means the function will simply "return" from anywhere I want.