Curtis is right... modelbuilder is a fine tool in the formulative stages of a workflow. On the upside, the image it produces is really nice. On the downside, the more people play with/edit a model the more discombobulated it becomes and parameters get out of order and errors begin (note... they can be reordered, but a novice user may not know this).
Even if they manage to get it to work, disappointment often sets in when it doesn't work on another computer or with different inputs. The trick? Once you get it to work, spit it out into a script, turn the script in to a script tool so that your parameters can be overtly specified and check by the tool and your selection of inputs is controlled. The tool and its associated script(s) are readily distributed and they can be extensively documented in their help (that expand help button).
I have blogged on options before, including how to move from modelbuilder to scripts and even more simply, how to turn the outputs of the Results window into scripts. The basic toolbox tools are the way to go for the vast majority of workflows that I have seen on this site.