acquisition Sparrow working on this update. The UI has been redesigned to be cleaner and easier to navigate, and look a lot more like Google's web products, which got a unified UI update earlier this year. The app also has a new welcome experience to walk you through all of the new features. The app feels more fluid, but it does still rely on some HTML wrapping rather than native elements, so message viewing can still feel off.
The big update for many people is that Gmail for iOS now handles multiple accounts, which has been something that users were really disappointed was missing in the initial release. On top of that, Google has added predictions when typing a Search query, added infinite scrolling to the Inbox, and added some better integration in messages.
Users can now reply to Google Calendar invites right in the message view, and if you get a link to a Google+ post, it will open in app with options to +1, reshare, comment, etc.
If you want to give Gmail for iOS another shot, it's available for free in the iTunes App Store.