Padvance reviews the re-released official Gmail app for iOS and comes away disappointed. Parisa Vassei writes, "It fails to provide support for iOS 5's notification center and overall behaves much like an enhanced version of the Gmail web app which is acceptable (I guess) but also rather disappointing." More details and criticisms can be found in the full review.
But you can still go back to the old layout if you prefer.
Overall, this looks like a decent UI update for people that use multiple Google services.
Spam runs rampant on Gmail, but you have options.