As someone who isn't following the Qt vs. GTK debate closely, this makes me ask myself why the choice of a code library -- which should be based on how well it

As someone who isn't following the Qt vs. GTK debate closely, this makes me ask myself why the choice of a code library -- which should be based on how well it fits into application code and similar criteria -- affects the user at all? If the user is able to spot the choice of toolkit just by using the application, I'd suspect that design decisions have been coupled to code decisions, which would be a smell by itself. I mean, what exactly would you do if the code guy says, GTK fits the code best, and the design guy says, Qt fits the design best? The answer would be "the Qt look-and-feel for design, and the GTK API for code", but you can't do that when you have coupled these decisions.