Guitar Hero: On Tour might have been enjoyable if the hardware wasn't a complete and utter pain to use.
In a perfect world a portable Guitar Hero with a grip and a small but enjoyable setlist would be entertaining. Unfotunately, everything it attempts to do is flawed. The problems start with the hardware.
There's no real way to explain it. The guitar grip is just impossible to use. You can support your DS using the strap, but it constricts your fingers. You can remove to strap, but you'd then have to palm it, which hurts your thumb. If you hold the DS slanted, it can give you cramps. If you hold it straight, you'd have to keep your elbow and shoulder upright and completely stationary. If you're at home, you can lay down and rest it on your chest for optimum control, support, and movement. But if you're at home, you can also play regular Guitar Hero.
You use the colored buttons to hit the corresponding notes just as you normally would, and you strum using a pick stylus. It sounds feasible, but it's always cramp inducing no matter how you look at it. There's simply no comfortable way to play it. The strumming also dosn't always register when you're going back and forth extra fast, so attempting to beat the tough songs is usually filled with fake difficulty.
The setlist has some pretty good songs, but for every good song there's usually a bad one, and at 25 songs total, it's not a good ratio. Maroon 5 and Smash Mouth stick out as inapropriate for Guitar Hero no matter what your taste, and there are 5 songs we've already played before on Guitar Hero 3. It seems as if On Tour was not designed to expand the Guitar Hero experience, but make it portable. If you're looking for depth, you'd be disapointed.
Guitar Hero: On Tour is a challenging affair in its own rights, save for the challenges with trying to hold the thing in the first place. Try it yourself. If you can somehow bear the physical pain it induces, then you may enjoy it after all, although 25 songs for the $50 price tag still isn't a great value, portability considered.