Paul Thurrott posted a review on Apple iOS 4
Apple's fourth generation mobile operating system, renamed just before launch from iPhone OS 4 to iOS 4, is the standard by which all other mobile systems must be judged. And it's a high bar: The iOS has matured from an amazing but deeply flawed platform to one that is both easy to use and achingly powerful. It's so good, in fact, that's it's taken the rest of the mobile device industry years to catch up. (Only Google's Android seems to have surpassed iOS in any meaningful way so far.)Apple iOS 4 Review
With iOS 4, Apple of course hopes to extend its lead and raise the bar yet again. Not to pull a Walt Mossberg here, but I've been using near-final versions of iOS for several weeks now on various Apple devices, including an iPhone 3GS (before it was stolen), an iPhone 3G, and a 3rd generation iPod touch. And while I'm still looking forward to getting an iPhone 4 as soon as possible, and to the eventual iOS 4 version for the iPad, it's already clear that Apple has a hit on its hands.
