The instruments themselves are fantastic, but the game's setlist, DLC, and mechanics lack considerably.
Let's start with the instruments. The World Tour guitar offers a wider strum and whammy bar, an accelerometer that makes activating Star Power no longer an accidental occurrence, and a "touch strip" below the buttons that allows players to slide their hands along the strip to "catch" some specialized notes. These passages of notes are called "slide sections". However, the touch strip is rendered nearly useless since all of the notes in a slide section can be hammered on without even pressing down on the strum bar. The slide strip also has no tactile marks on it, so you never know where your hand is located on the touch strip at any time, so buying the guitar just for the touch strip isn't really worth it in the long run.
The drum kit is silenced and features two raised cymbal notes, and is miles better than the Rock Band kit.
The singing, however is done very poorly, but I'll get to that in a second.
It's the gameplay mechanics where Guitar Hero really suffers. Part of that is probably due to the fact that while Guitar Hero and Rock Band have basically the exact same concept, Guitar Hero still tries to be different from Rock Band, and changes things that don't need to be changed. For example, when your band mate fails out, so does the entire band. That's it. No reviving band mates with Star Power, no nothing. It's just over. This is made even more frustrating by the fact that Star Power is a shared pool, so you can no longer save up your own Star Power and use it on failing band mates. Each band mate has to use it themselves in order to save themselves from failing a song, which defeats the entire team-based aspect of the game.
The game's setlist is utter garbage in comparison to past Guitar Hero games. Out of the 80+ songs on-disc, 60 of them aren't really that fun to play on guitar, and hardly any of them are challenging in the slightest. Players of Guitar Hero III that could never make it past the last setlist probably take this as good news, but it truly zaps away the challenge of what makes Guitar Hero, Guitar Hero. Even the songs that could've been challenging are unnecessarily simplified by slide sections that can be hammered on even after missing a note. Not to mention there are 3 or 4 SPANISH songs. Seriously? "La Bamba?" "Escuela de Calor?" Since when did I need to play through a song in a foreign language to get to the good songs I actually WANT to play?
The singing is ridiculously inaccurate and on higher difficulties, you can basically forget about hitting any of the notes correctly. It's just impossible. It's difficult to follow whether you're singing too high or too low, and the game isn't afraid to fail you into next week when you miss a couple lyrics. But hey, there's always the fun beginner mode where all you have to do is say the words without getting the pitch right at all. You can basically make it through the singing career mode by rapping every single song on the disc if you didn't want to deal with singing on-pitch.
Also, The song creation may have sounded good on paper, but in reality it just doesn't stack up. Amateurs are going to have a couple minutes of fun screwing around and jamming freestyle, but anyone without music experience making their own song is going to sound like the textbook definition of death. The sound samples are pretty awful, too, which just makes things all the worse. Luckily, the GHTunes service allows you to download other, much more experienced people's creations to your disc, but in all honesty, it's a feature you'll probably forget about eventually anyway.
As far as DLC goes, it's an absolute joke. It's almost even worse than the on-disc setlist. The only decently good things on there are 3 Queen songs, Boston's "Rock and Roll Band", along with 2 or 3 other classic rock songs, and Metallica's "Death Magnetic" album. The rest is a mixture of free songs that should already be on the disc in the first place (Ted Nugent's Guitar Battle), 4 or 5 European track packs loaded with songs not even representative of the music in Europe, and new songs from bands whose old songs are miles better (new Eagles songs as opposed to old ones? Meh.). Heck, they hardly even update the DLC anymore. It's incredibly frustrating.
All in all, Guitar Hero: World Tour still has the Guitar Hero "feel" about it, but it just doesn't stack up to the quality of its past games, or to the quality of even the first Rock Band game. The harsh gameplay mechanics and simple slide sections don't blend into the formula that well, and while Guitar Hero's off to the right start, they still have some ground to cover that Rock Band's had covered for nearly 2 years.