Up to this point, even the answer "it's cheaper" hasn't been possible, since most other devices actually cost as much, or more, than an iPad.
Amazon's Kindle is the first device that answers the question, and it is not about "speeds and feeds."
Both the iPad and the new Kindle Fire are gateways to a rich content ecosystem.
That’s the difference that other tablet makers missed. Motorola, Samsung and Research in Motion have essentially been chasing the iPad on specs, building the best tablet they can manage at the same starting price of around $500. Watch Jeff Bezos introduce the Kindle Fire
The Kindle Fire is the first device with a good answer. It is much cheaper than an iPad and offers a digital content ecosystem that rivals Apple’s (fewer apps, but more books).
Also, Amazon built an alternative to the iPad, rather than a direct competitor. That's why some might say the Kindle Fire is something different. It is sort of an iPod "touch" content consumption device with a more-usable screen, that is optimized for multiple content types, including reading books and magazines, video and audio, plus web browsing.