Barnes & Noble is also rumored to be launching a 10-inch version of the Nook Color before the end of 2011. It is , and will give Barnes & Noble a head start against a larger Kindle tablet for users who prefer the 10-inch tablet form factor. Amazon's Weak Spot

For all of its potential advantages, the Amazon Kindle tablet also faces challenges.

First, just as there are those who prefer the 7-inch form factor, there are those who do not. At 7 inches, the display has significantly less real estate than a 9- or 10-inch tablet, yet it is still too big to fit comfortably in a pocket. It is possible that Amazon chose 7 inches to intentionally avoid direct iPad comparisons, or to make the device more appealing to the Kindle e-reader fan base.

Customizing Android could be brilliant, or it could end up being Amazon's Achilles heel. Customizing Android enables Amazon to create a tablet experience that is unique to Amazon -- setting it apart from the array of rival Android tablets and putting Amazon in control of updates rather than waiting around for Google. But, the burden will be on Amazon to continue to develop and maintain its custom OS, and splitting off from the Android pack could lead to app compatibility issues -- especially as Android moves to its next-generation operating system, Ice Cream Sandwich, later this year.

The other pitfall is the same one that plagues every tablet on the market -- it's not an iPad. Apple dominates the tablet market with the iPad, and it is a dominant player in the smartphone area with the iPhone. The popularity of iOS is a self-perpetuating cycle. Millions of users are already invested in the Apple iOS ecosystem, and convincing them to break ranks and start over on a new platform is a daunting challenge.