Despite its flaws, Dead Head Fred is still a great adventure game.
Combat is fairly simple; you keep pressing the square button for an endless attack of punches or square followed by X to do a variation of it, and even though Fred's heads gives you different special moves combat is still superficial and repetitive. The heads true purpose is to solve the game's various puzzles, such as using the zombie head to fill it with hot air and reach normally inaccessible areas or to fill it with water to put out fires; and since you wont get all the heads till late in the game you'll be doing a lot of backtracking to get all those stuff you saw before but never knew how to get; giving the game a lot of replay value.
You'll also come across various mini games scattered throughout the Bars or other shops, such as playing pool, a pinball machine and even cock fighting. But while these games do offer a little variety from the main adventure, none of them have any lasting value for their simplicity.
What really makes the game stand out from other adventure games is the story's dark humor that uses its fair share of profanity; and there's also Fred himself. He'll often have some snappy comment for every situation which makes him one of the best characters ever seen on the PSP.
In short, Dead Head Fred has the length and clever puzzles to attract adventure fans and enough black humor to appeal to the older gamers, it could have been better in some parts but it's still one of the most unique games available on the PSP.