Doesn't work with notifications currently, so it only works when you launch it?
I don't believe the Google Search app has ever integrated with Notification Center, so hopefully they are working on adding that.
I would just hope that Google embraces Notification Center instead of half-assing it like they're doing on other apps. For example, using the stock mail app, I can turn on/off notifications per account, show how many emails I want to see on the lock screen from each account, decide to show a preview or not, and choose what sound plays.
Gmail, on the other hand, take a very Android approach to notification settings. You can have them, or you can't. You can't selectively choose to get notifications from different Gmail accounts, I can't set a limit on the number of emails notifications I get on the lock screen, I can't set a different notification sound and I can't turn off the preview.
The Notification Center integration, or lack thereof, is the only thing keeping me on using the stock mail app, when I'd much rather be using the Gmail app.
So I hope when notifications are put in for the Google Now, that I can turn on/off notifications on a card basis. Sure, I'd love to know when I need to leave for an appointment, or how bad traffic is when I go to leave work, but I don't really need to know the instant the Spurs win a game. Some people do, and that's why I'm hoping Google will embrace the NC rather than shun it.