All of the tables I've owned have been fanless and relatively noiseless (the Toshiba had a spinning drive, but at the time that was the technology). Need I point out the N700/800 series, no fans or noise there. Both the JooJoo and the U1 are solid state and fanless as well, both weigh about the same as the iPad, and have just as much processing power (if not more). Again, the iPad is nothing new. It's just the first time you can get it with an Apple logo on it.

Tablets have never sold well, mainly because it was hard to do anything on a computer without a keyboard. With touch technology, and better designs I think we're getting close to a design that people may be able to use. That, and the nature of computing is changing, from being a work/input device to being a consumer/output device. Less need for input (or a better way to do it, like speech recognition) will drive the tablet closer to mainstream.

And that's the million dollar answer. The only reason the iPad has seen the sales it's seen has been because it has an i in front of it's name. If you'd released the exact same hardware and software, but put "Dell" on the cover, it wouldn't have sold a tenth of it's current volume. The iPad is riding on the coat tails of the iMac and the iPhone.

I do think the iPad has had a positive effect on the tablet market in general though. As more people realize that giving up the keyboard doesn't mean giving up your ability to submit your input to things, attitudes about tablets will change. In that regard the iPad has been a game changer. But make no mistake, the hardware and the concept is not new by any means.