Played it at a friends house yesterday. There are so many things that they changed just for the sake of being different from rockband, most of which are for the worse.
You have to pay your money you make in the game in order to play the tool songs, so even though you have the unlocked from a very early point in the game, you need to pay 8,000$ for the venue (tool won't let activision have fans/avatars playing their songs, they require to only have art in the backgrounds).
All of the menus are a bitch to navigate, you have to select your difficulty in a separate menu before choosing songs, the text does the same annoying shit as the notes, where they light on fire when selected.
Don't even get me started on vocals, being able to "full combo" a song when only getting 80%? Instead of doing it by phrases and giving some leeway like in rockband, they do straight percentages where you have to hit 100% of every single word in every single phrase. They also have freestyle sections in place of cowbell/tambo/clapping sections, but these freestyle sections are still graded and required.
(Satch boogie is one of the hardest songs in the game but it is an instrumental, but still has lyrics).
Drums you just have to be close you'll get it, the window for hitting them is so wide its ridiculous, you start to feel disconnected when its as easy as it is. Having to activiate star power using Y/B (using my old, broken rb1 set because my ION kit doesn't work) is a pain in the ass.
Bass has open notes, but on most of the songs it is very boring on bass and you will likely be stuck on it for as long as you play, because you have to go to a separate menu to change to guitar.
Instead of a single band member failing or using starpower, they are as a full band. This means that if one person fails (in some cases people go from fine to failed without even knowing it, because the meter is usually on the opposite side of the screen from you. It is hard to tell if you have overdrive because you have to look at the left side.
The setlist is alright, though it has more songs from 2000+ which I really don't care for.
Oh yeah, if this video doesn't sum up what the song creator is used for, I don't know what will.
YouTube - Guitar Hero: World Tour - Guitar - WTF (Custom song). Pretty funny, must watch