There are four apps in the dock of my iPhone. For years, they were all made by Apple: Phone, Safari, Mail and iPod. Now, two of them aren't: Rdio replaced iPod/Music last year, when I moved my music collection to the cloud; and Sparrow replaced Mail today, because it's awesome.
Sparrow started as a desktop app for Mac, meant to replace OS X's tired Mail.app. It was unbelievably good, assuming you used Gmail, and people immediately started calling for an iPhone version.
Mail for OS X looks like Outlook; Sparrow looks like a Twitter client. Mail for iOS looks like it did the day it was announced in 2007, and like all the first-wave iPhone apps did; Sparrow for iOS looks like Tweetie, or Path. It has pull-to-refresh. It has a a threaded message view that makes sense. It has a card-flipping navigation system that moves you from folder to folder almost instantly. It feels like iPhone email should feel after four years, and makes you wonder why Apple's left its own app – arguably the most important one on its phone — to wither.
The one thing this app doesn't have? Push. I'm a habitual email checker and a compulsive pull-to-refresher, so this doesn't really matter to me. I'm sure it'll be a dealbreaker for some people but still, give Sparrow a shot. It's three bucks and it fixes the single worst thing about iOS.