As planned, Steve Jobs gave the first demonstration of Apple's next mobile operating system this morning. Mac sites and gadget blogs are rife with coverage, and the folks at Engadget even put together a nice live blog of the event, complete with quotations and a wealth of photos.
Jobs presented major additions and improvements as "tentpole" features. There are seven in total: multitasking, folders, an improved e-mail client, iBooks for the iPhone, new enterprise functionality, Game Center (as Engadget puts it, "Apple's got their Xbox Live"), and iAd, an advertising scheme for third-party iPhone apps. We can also see a slightly upgraded user interface, with an iPad- and Mac OS X-style reflective shelf at the bottom. Apple's iPhone OS 4 page points out more than 100 new features, though, so these are just the highlights.
iPhone OS 4 will be out this summer for the iPhone 3GS and the latest iPod touch, while iPad users will have to wait until the fall—but they will get multitasking nonetheless. Folks with iPhone 3G and second-gen iPod touch devices won't be so lucky; they'll still be able to upgrade to iPhone OS 4, but without the multitasking goodness. Apple apparently made a big deal out of iPhone multitasking's performance and battery life implications, so perhaps the iPhone 3G's hardware simply isn't up to the challenge.
iAd also sounds like a big deal, since it may help keep third-party apps free with consistent, purportedly elegant advertising. iAd will run natively on the iPhone OS and let users click ads without leaving the application they were using. If the Apple demos Engadget covered are the shape of things to come, iAd will also allow for surprisingly interactive ads, some with their own little mini-games and HTML 5 video. Apple will reportedly sell and host ads itself, splitting revenue "60/40" with app makers.
iPhone OS 4 isn't going public for a few weeks, but developers can already get their hands dirty. A beta of the iPhone SDK 4 is now available from the iPhone Dev Center page. If you're not already a member of the iPhone Developer Program, though, you'll need to shell out $99 for the privilege.
Update: Apple now offers a QuickTime webcast of the iPhone OS 4 launch event.