I've been teaching an Introduction to Perl Programming for five or six years now, and have been introducing perltidy early in the class as one way for students to meet the style requirements for their assignments. It really does a great job at cleaning up messy, poorly formatted code.
On the other hand, if the input file is already well organized and well formatted, perltidy has a tendency to actually mutate the input for the worse.
p.s. Just created a new Perl course at Foothill College called ... "Intermediate Perl Programming" ... no, really, I thought of it all by myself.
Can't wait for the last of the trilogy!