Google Now for iOS has most of the features from Google's Android app and plenty of customization options that aren't available in the Android app. There aren't many missing cards: research topics, activity summary and events nearby.
I was surprised to see that Google added a lot of settings that let you tweak each card. For example, you can customize the traffic card and decide when it appears and the transportation mode for commutes and other trips.
Since most Google Now cards use location data, it's obvious that Google wants to update your location even when you're not using the app. "Location Reporting helps Google Now show you cards related to traffic alerts, directions, and more. Turning on Location Reporting allows Google to periodically access your location data, even when an app is not in use. If you have Location History enabled, reported locations are stored in your Location History. (...) Since Location Reporting has been optimized to use GPS as infrequently as possible, there should be minimal impact on your battery life." Location Reporting can be disabled from the app's settings section, while Location History can be disabled from the Google Latitude site.
It's interesting to notice that Google Now for iOS is placed less prominently, at the bottom of the screen. You need to swipe up to see the cards. Google Search for iOS doesn't show notifications yet, so you need to constantly open the application to see the new information.