As expected, iPhone 3G performance improves considerably when running iOS 4.1 in an informal speed test.

Lifehacker has posted a video comparing an iPhone 3G running iOS 4.0 with one running iOS 4.1. In the "tests," which are shown side-by-side, iOS 4.1 bests iOS 4.0, sometimes by as much as 10 seconds.

iOS 4.1 won all four tests, which involved sending a text message, locating a store in Google Maps, displaying a photo, and loading a website. The tests were conducted on a single iPhone and then stitched together. The version of iOS 4.1 used was a "final release" version.

In testing, the most noticeable difference was "UI responsiveness." The UI for iOS 4.1 "didn't get stuck nearly as much" on interface elements or when entering text.

Apple Chief Executive Steve Jobs announced Wednesday that the iOS 4.1 update will ship on Sept. 8. Jobs specifically mentioned iPhone 3G performance as a "bug" that would be fixed with the update. Long-awaited proximity sensor and bluetooth fixes will also be included in iOS 4.1.

Users who upgraded to iOS 4 on their iPhone 3G have reported serious slowdown of their phones, with some units becoming "unusable." In July, Apple told the Wall Street Journal that it was aware of the reports and looking into the matter.