There's a little more detail in the neck (it has fret markers now), and the buttons are less "spongy" than before. Also, although overall build quality is stronger and sturdier, with a quick flip of a recessed level on the back of the guitar, the neck can actually be detached from the body entirely. VP of Hardware Lee Guinchard made a quick, cryptic reference to this giving Red Octane "future possibilities" down the road - (maybe a longer, bass neck?) - but the obvious win is that it should make transport and storage a bit easier.
While you're flipping switches in the back, you'll notice there's a second one that releases the guitar's faceplate - you're no longer bound by one, two, or even ten colors. You can swap them out at will, going from lightning bolts and skulls at your buddy's house to your special Hannah Montana custom plate at home. At last, you're free to be yourself.
Of course, all three versions of the guitar are wireless, though the PS3 version still uses a USB dongle (Sony wasn't making with the Bluetooth specs quickly enough, apparently). All three versions also sport an improved tilt sensor, with an accelerometer replacing the less-accurate tilt switches in previous models - the Wii version actually borrows the tilt-sensing abilities of the Wii remote itself, which mounts right into the guitar's body. The remote will also rumble slightly when your star power is ready, and makes that dreaded chugging "ping" sound when you miss a note.
The bottom line? It doesn't matter how cool your old guitar controller is - you now need this one. Retro gear might be cool in the real rock world, but here in the pretend one, you're going to want the latest and greatest. And this is it.