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As you can see on the ZDNet Gadget Reviews blog the specs for the Nook Tablet are very similar to the Amazon Kindle Fire. The differences are in the included storage (8GB vs 16GB + microSD card slot), processor (1 GHz vs 1.2 GHz), RAM (512MB vs 1GB), and the standard EPUB and Office document support in the Nook Tablet. If you just looked at the specs, then you may want to shell out the extra $50 to get the Nook Tablet. However, as we have learned from Apple, mobile is about much more than the specs.
The ecosystem and user experience is what differentiates devices today and Amazon is a major player in the ecosystem for the Kindle Fire. However, Barnes & Noble has partnered with Netflix, Hulu Plus, Pandora, and others to bring an ecosystem to the Nook Tablet as well. I will rarely use the device for ebook reading since I find a dedicated eInk device with no distractions to offer a far more compelling reading experience.