lagging behind Google's offering overall because it's place database is far smaller, and it doesn't include Street View, or public transit directions and info. There is a way that public transit info can be hooked in by a 3rd party service, but that doesn't yet exist. Google has promised a version of Google Maps will be coming to the App Store, but hasn't yet released it, so if you think Google Maps will be better for you, it may be best to delay the update until Google releases its app.1) No more Google Maps. Apple's new Maps app will give you turn-by-turn navigation, but the general feeling is that it is
2) No more baked-in YouTube. This isn't an issue for iPhone users, because Google has released an iPhone version of YouTube into the App Store, but iPad users won't have a YouTube app. This isn't such a big deal, since the YouTube website was better than the baked-in app anyway, but some people prefer apps to websites.
If you don't mind those two changes, then you can grab the iOS 6 update through iTunes, or OTA (on WiFi of course, since the update clocks in at around 500MB) on your device now.