Great peripherals and improved gameplay all around!
The Time Window
While the time window is no longer over-hardcore, it's almost too forgiving in this new iteration of GH. After getting used to the GH guitar a little more, I went hours playing guitar on hard without even 'going red' throughout the GH Tour Mode. This would never happen if I played RB2 at the same difficulty. At times, it felt like I was missing notes but would still be hitting them. This encourages decent players like myself to go up to Expert b/c, other than the more complex tracks, much of the songs can become a bore on hard, especially on bass.
The NEW Bass
Awesome!! Adding a fret-less note makes bass in GH4 a more realistic representation of real 6 string action. The differences, note-wise, between guitar and bass become more apparent when you step into Expert territory. This is where the fret-less note comes more into play and can be a challenge to keep up with at times, especially when trying to keep a difficult sequence going for the majority of a song.
The Peripherals
Physically, the new peripherals feel sturdy and durable, but issues did occur when signals crossed between the wireless devices. This was fixed by adjusting the connections and the issue did not occur again. My friend had mentioned a stuck red button on the guitar before I got to his house, but the problem never recurred. The drums are by far more silent, sturdy, and more fun to play than the first generation RB1 drums (I have not tried any new RB2 peripherals yet). Having raised cymbals really do immerse you more into the gameplay and the sturdiness allows you to REALLY wail on it without a worry in the world. The mic is less sensitive when it comes to tapping it, you need to hit it hard directly on the top of the mic. The guitar is a bit longer than the GH3 guitar and has a slightly improved strum bar. I did not bother trying the touch pad, but my friend enjoyed using it for the scarcely allotted sequences where it could be used.
Tour Mode
WOW! This has to be the best tour mode ever because of the inclusion of actual CINEMATIC SEQUENCES!! At the end of a venue's setlist, you will be asked to perform an encore which will trigger a special cinematic (whether in-game or not) including special guest appearances by famous rockers. ****SPOILER**** You will love the ending sequence that will begin what I consider the best song in the game accompanied by the credits roll.***** You will simply be blown away by the extra effort put in by Neversoft in this, what I consider, an actual story mode!
The Songs
GH has some great songs, some of my favorites being Pull Me Under by Dream Theater (!!!), Mr. Crowley, and a few I can't even name. The reason for this is because the majority of songs in GH are of the lesser-known variety. This is a sharp contrast from the big name setlist RB2 boasts on-disc and through DLC. The upside to this is that most of these unheard of songs are pretty fun to play and will give your fingers some work.
Graphics
Stylistically, I much more prefer RB2's clean and wavy templates over GH's messy, uninspired, and utterly cliche menus and score screens. There are no special titles like "top performer" or "most gutsy" as in RB, a feature you tend to miss when you get used to it. The character models thankfully look a lot less cartoony and in GH3, a trait I despised for some reason in 3. The special guest rockers look nearly identical to their real life counterparts and are instantly recognizable. The stages, on the other hand, have gone even more extreme, to GH's benefit, taking you places you would never expect even in a GH game. This lends to the excellent Tour Mode and these stages do play a part in the cinematics.
Overall
This is an excellent addition to the GH series, and comes close to taking RB2's crown. While the Tour Mode blows RB2's achingly long version out of the water in terms of having an actual story, the OVERALL song selection comes no where near the 300+ already available RB2 song library. The graphics in GH4 are decent overall, but do not compare to the trippy effects and superior character models of it's rival. With that said, Guitar Hero 4 has distanced itself even more from RB2 despite adopting the drums and mic, ensuring that it remain its own distinct rhythm game. The bottom line is, if you already have invested into the GH series, then GH4 may be the game for you. But if you have RB already, and have the money to blow, you won't mind getting access to one more Dream Theater song. =)