Among UNIX fans, `cat(1)' is considered an excellent example of user-interface design, because it delivers the file contents without such verbosity as spacing or headers between the files, and because it does not require the files to consist of lines of text, but works with any sort of data.
Among UNIX haters, `cat(1)' is considered the canonical example of bad user-interface design, because of its woefully unobvious name. It is far more often used to blast a file to standard output than to concatenate two files. The name `cat' for the former operation is just as unintuitive as, say, LISP's cdr.
Of such oppositions are holy wars made....