Not a shock IMO. After hearing about the Aerosmith one, I figured these would be a 2-3 per year occurence on top of the regular GH games released yearly. They can literally do up a song in a matter of days so it's not a huge undertaking for them.
It a way it's not a bad idea. I mean, if you really like the band, and many love Metallica or Aerosmith, you're likely to find you like at least half the songs, which is more than you can say for the regular GH games. And it'll be cheaper than d'loading individual songs since they're running at just over $1 a song on these compilations. And hey, if you don't like the band, you can just ignore these ones. The only thing over and above the regular GH experience is going to be the band history stuff. But fans may still love them. I may be interested in used copies at $35 each or so depending on how good the songs are.
It ain't gonna slow down any innovation they're gonna have with the regular GH series. They know Harmonix is on top of them and they're gonna have to come up with new stuff to keep up. I do think the drums may actually end up being better in GH but not enough to warrant a purchase over the Rock Band ones. And I ain't sure how Konami's gonna make ground against two big franchises with Rock Revolution, they're really gonna have to come up with something good and different.
At the end of the day, I'll probably stick with Rock Band a bit more but I'm certainly not against any quality GH spinoff ones. There's TONS of SHIT available for Rock Band downloads but that's not a bad thing. It appeals to others' tastes (as horrid as it may be). As long as the games maintain the quality in the music-related department (IMO, GH3 and to a smaller degree GH2 became more games than playing music; that's not good), I'm OK with it. It'll just come down to personal choice and even if I don't like it, the more the better
I was there on that fateful day, were you?