OK, I recently got this as a present for my birthday, and I'm highly surprised that this actually works! It's fairly simple to use - you slide it in the GBA option pack, and all you do is slide your hand in. simple as.
Rather than spouting out why I love it so much, I thought I'd go for something a bit more condescending. There ARE problems with this game. Being a Guitar Hero fan, I absolutely love getting hold of the guitar, sticking it on expert mode and rocking until my hands hurt an hour or so later. With this, however, you don't get that same feeling. For a start, there are only four buttons instead of the normal five, which makes it much easier than the previous games.
Since it's on the DS, you don't have much of a screen to see everything properly. The combo meter is on guitar side of the screen, which makes it difficult to see what combo you're on, which then makes it difficult to determine when to use the star power. On the matter of the star power itself, you have to make a noise into the microphone of the DS. Anything you say however is usually just a distraction. I find it best to whistle at it.
Getting back to the 'feel' of the game, as I find myself whistling at it, I can only imagine I'm playing a trumpet instead of a guitar. Maybe they should rename it Trumpet Hero!
The song choices were also supposed to be a new set list. Unfortunately, that's not completely true. Some of the songs are simply taken from the guitar Hero III, which is fine from me, but some other people may complain, especially when this game delivers a different experience from the others, and in my opinion, should then have different songs, at least.
Another fault I quickly found is that if you accidentally, "Rock too hard" and knock the hand grip, and buttons peripheral out of the GBA option port, then the game will stop, and you lose your current data as it asks you to turn the console off. It does NOT let you simply plug it back in again.
Now, about those times. Most guitar hero players I know, like to play it for anything between an hour for up to 4 and 5 hours. The reason? It's incredibly FUN! In previous games, you have your guitar; you're standing in front of the usually big TV, which pumped up sound system to give the affect of being a rock star. Guitar Hero: On Tour, however, gives very little to create this affect. The DS has small screens, with Video out for obvious reasons - but still, it has terrible speakers, which if you want to hear a decent sound, you will have to plug in headphones, which severely limit you're rockin' experience, and the guitar peripheral severely cramps your hand much quicker than the guitars would in previous games.
Now don't get me wrong, although all I've wrote about so far are bad things about the game. But there are some things in it. For instance, there is a slightly higher level of customization in this game than there is in the others. For instance, if you change your guitar, it will change the guitar IN-Game, and since one screen is dedicated to the strumming, you get a nice image of your guitar. That's about it though.
The main advantage this game has going for it, is its amazing sense of portability! IF you're going out on a road trip, or are simply going to be somewhere where you aren't able to get to your not-so-portable console, then this is a great game to take along and kill some extended time.
Overall, it still holds up as a GH game, and its portability factor certainly sets it apart from the others. But if you want the proper GH experience, then Guitar Hero III is a much better choice at the moment, and let's not forget the soon to be Guitar Hero V.