I've done rolling deployments but also a similar but different way at Yahoo!.
We have access to multiple colos of slightly over-capacity machines. It's not uncommon to migrate by switching all traffic over to one colo. Then upgrade the next colo to the new code and switch all traffic there. Finally upgrade the first colo and then start cross loading the traffic between colos again.
Since we are big enough to have at least a couple of colos per geographic region this means we can avoid rolling migrations which are pretty horrible when you get trapped in a failure mid-roll.
We have access to multiple colos of slightly over-capacity machines. It's not uncommon to migrate by switching all traffic over to one colo. Then upgrade the next colo to the new code and switch all traffic there. Finally upgrade the first colo and then start cross loading the traffic between colos again.
Since we are big enough to have at least a couple of colos per geographic region this means we can avoid rolling migrations which are pretty horrible when you get trapped in a failure mid-roll.