What do you know? McGraw-Hill CEO Harold McGraw was on the money yesterday when he said Apple would announce a tablet on Wednesday. The iPad now has officially arrived, weighing in at less than a kilogram, with a 25-centimeter LED-backlit display that is just over a centimeter thick. It will be available by the end of March with a price tag starting at $499.

The iPad, which marries a tablet computer with an electronic book reader, is less about cutting-edge technology and more about clever ways to package that technology to deliver a variety of content. Tablets have been available for nearly a decade (the concept of an electric clipboard goes back even further) and the e-reader market already has several success stories, most notably the Amazon Kindle.

From Apple's description, the iPad is essentially a continuation of the multimedia and communications technology the company has been making since it introduced the iPod in 2001. Now, in addition to having a mobile, multi-touch screen device for listening to music, playing video games, e-mailing and surfing the Web, Apple fans will also be able to read electronic books with the help of the new iBook application (books bought through the new iBookstore, of course). The book that Apple CEO Steve Jobs demonstrated during his presentation at the iPad launch event on Wednesday costs $15.

Jobs made sure to acknowledge Amazon's role in popularizing the e-reader, adding that Apple would now "stand on their shoulders" and go farther, TechCrunch reported.

Tablet PCs have been a hard sell, which is likely why Apple chose not to use "tablet" in its new product's name. Tablets introduced by Acer, Compaq and others in the 2001 timeframe had some interesting features in their time, including handwriting recognition that could (usually) convert stylus scribbles into readable text or could display digital doodles and diagrams. But that generation of tablets (which sold for $1,500 or more) was primarily designed to use the Windows operating system and function as a next-generation laptop rather than a multimedia device for reading books, playing video games and watching video.

Microsoft has taken up with Apple's competition in the emerging market for e-reader/mobile multimedia devices. During his keynote at the Consumer Electronics Show, Microsoft CEO Steve Ballmer demonstrated a number of new "Slate PC" devices running Windows 7, which will go on sale later this year. Ballmer called these Slate PCs (there were devices from Hewlett-Packard, Archos and Pegatron) "almost as portable as a phone and as powerful as a PC running Windows 7." The Archos 9 PCtablet sells for $550, but the HP and Pegatron's devices exist only as prototypes at this time.  

Apple also appears to continue to respond to critics such as Greenpeace, which has cautioned consumer electronics vendors against the use of toxic materials when making their gadgets. Jobs also pointed out that the iPad is free of arsenic, BFR, mercury and PVC, and is "highly recyclable."

Every iPad has Wi-Fi and some models will also offer 3G connectivity to the Web (those models start shipping by the end of April and will cost as much as $829). Battery life is expected to be up to 10 hours. Under the hood, the iPad runs on a 1-gigahertz processor called the A4 and can have up to 64 gigabytes of storage. Data plans are available through AT&T without iPad users having to sign a contract.

iPad image courtesy of Apple