Manpower is pretty and costs $25.
Man Handler is freeware. http://www.versiontracker.com/dyn/moreinfo/macosx/29876
Man Handler prints too, and can save to PDF, too (is that important?) via the OS X print dialog.

Manpower does everything it says it does. The only real, functional difference I can find in casual use is that it divides the commands into categories (User, System, Library, File, etc.) and has a brief description of what each command does available before clicking and viewing the individual command, while the free Man Handler requires the user know what command he's looking for, and to type the command name into the input field.

Manpower is offered with a 30 day free trial license.

If Manpower's developer was asking for five bucks for packaging this freely available info, I wouldn't have posted this note, but $24.95 is not reasonable.

Try them both. Keep the one that makes sense for you.