On top of the new icon, Version 2.4.1 of the app includes an “enhanced attachment experience,” which really means that a larger image attached to an email will now open in a new full screen viewing mode when tapping its thumbnail.
The update also includes improved integration with other Google apps:
Better integration with Google apps – Google Drive and Google+ links go directly to the app, if installed. You can turn this off using the in-app settings.
Gmail version 2.4.1 for iPhone and iPad is available on the App Store now.