Mere consistency is not enough. List is hard to read because humans do not have a natural feel for how deep a set of nested brackets are, and you have to be able to spot the matching open-bracket to understand the code.
Again, it's hard to read if you are not familiar with it. Even as someone relatively new to Lisp, indentation and formatting makes a world of difference for readability.
This isn't specific to Lisp, either. I posit that if you took your average C-like and removed indentation from any reasonably sized function or method (one or more loops, one or more if/else), you would have a hard time counting brackets.
I agree that consistency is necessary but not sufficient, though, which is what I think you're getting at. Most of the time, though, consistency is clearly better than inconsistency. There's less to remember or, if you prefer, less to screw up. :)
