Better late than never, I suppose...
We put a few hours into Rock Band last night and I came away feeling that it had met my lofty expectations -- although, strangely, I was not as awesome at playing the drums as I had been in my dreams the night before. It's that damn kick drum: either I hit it every time I hit one of the pads, or I forgot about it all together. Hitting the correct pads with the sticks is not too difficult to pick up. (What's a good synonym for "hit" in this case, anyway?) I can imagine the drums being more rewarding to master than the guitar parts, because it's more of a transferable skill. You will have to develop a sense of rhythm to play them well, and play them using much the same mechanics as playing real drums. I want to do a lot more of this.
Playing the guitar required a bit of an adjustment, thanks to the new peripheral itself, and the different design of the note charts. The biggest challenge for me was the lack of any space between the fret buttons. I usually use those to orient myself when shifting my hand position up or down the neck. The strum bar is much different, as well: without the obtrusive "click" of the Guitar Hero strum bar, I found it hard to tell if I was doing it right. It was a bit like driving an unfamiliar car: you need to orient yourself to the little things, but you're not in danger of veering off the road. And there's no question that the Stratocaster design is the most aesthetically pleasing of all the plastic toy guitars.
Singing was the most problematic aspect, and here's why: it was the place where it was the hardest to lose myself in the rock fantasy. When you play the guitar in Guitar Hero or Rock Band, your input doesn't result in something that sounds like the guitar part -- it is the guitar part. The drums are a bit worse in this respect, because even though you hear the correct drum sounds on the soundtrack, you also hear the click-clack of your sticks hitting the pads. While singing, I was aware only of the limitations of my own voice. Which is not to say that I didn't enjoy it, or that I didn't throw myself into it (particularly the optional yelling parts). Just that of everything I did in Rock Band, singing was when I felt the least like I was rocking thousands of worlds in a packed arena, and felt the most like I was in my friend's living room playing make-believe. Still better than any other karaoke game I've played, by far.
Better than a certain other recent guitar game, too.