I don't know why everyone has a problem with GH: On Tour. It does exactly what it sets out to do and it does it well.
The setlist is eclectic and good enough. The high points are "Breed", "Jet Airliner", "What I Want", "I Don't Wanna Stop", "Anna Molly", "China Grove" and "Jessie's Girl". The inclusion of songs from previous GH games seems silly and a waste of memory space. Also, outside of "Hit Me With You Best Shot", the returning songs are pretty weak. The only songs tha feel out of place are "All-Star", "Helicopter", "Heaven" and "All the Small Things" The songs are obviously dumbed down for the DS but you will get used to the sound quality pretty quickly since it's not horrid.
Those of you who are worried that the lack of an orange button will render the game "too easy" can calm down. "I Know a Little" and "Knock Me Down" are two of the hardest songs I've played on ANY Guitar Hero game. There are more triple notes and a few quadruple notes.
Overall, I am hugely impressed with how On Tour turned out. I'm bummed by the short setlist, but that's due to the DS cart's limits not the game itself. Also, keeping a multiplier on the higher levels is pretty tough, due to the strumming, ad the rapidness of the notes, but if you own a DS and you love Guitar Hero, buying On Tour is a no friggin brainer.