The video up top shows off some of the tweaks and additions made to GH5, but even the smallest ones really need to be seen in action to understand what they bring to the experience. There's small stuff -- new gameplay mechanics -- and larger changes that affect the way you'll approach the game.
One of the most basic additions are "band moments" -- sections of the song with fiery notes which, if everyone playing nails them, significantly boost the band's score for a short period (and make the screen look a little more intense). Another is the revival mechanic, which allows players who've failed out of a song to rejoin if the rest of the band can play well enough to "win over the crowd." Pretty basic stuff, especially if you're familiar with that other band game. (No, we're not referring to Rock Revolution; our apologies to the two of you who own it.)
In terms of more significant changes, we weren't able to spend a lot of alone time with the game, but we did catch a glimpse of a few challenge screens detailing the various (sometimes wicked-hard) things players will have to pull off in order to unlock new outfits, instruments and other items. This seems like a really nice touch for hardcore fans who will now get more than just a higher score for absolutely mastering each track.
Other than this and various instrument configurations (the four-guitar setup was nowhere as interesting or intense as the four-drumkit demo area, which was, as you'd expect, very loud) the Rockfest mode of the game was a major standout. It was being used as part of a competition to win one of Logitech's premium Xbox 360 guitar controllers (we tried to win one for you, the Reader, but the Score Hero guys were just too much for us) and was as fun as Activision was billing it. Of the various rule sets, we encountered a simple "top score wins" match, along with one that rewarded the player with the most consecutive notes for a certain potion of the song. Another featured a score multiplier that kept increasing as long as no notes were missed.
Apart from the ability to import songs from World Tour and Smash Hits -- as well as use GHWT DLC in the game -- the challenge unlocks and Rockfest mode seemed most exciting to us. Well, nearly the most exciting. That honor goes to the Wii version's Roadie Battle mode, which we'll talk more about in detail in a separate post. (Seriously, it was that good.)