Well, in terms of gaming, it is the most powerful tablet since nVidia manufactured the Shield Tablet to provide the consumers the best experience in gaming. It has near stock Android OS and few additional features, unlike Samsung tablets' UI which partially slows the system down.
In terms of productivity, others are better, Samsung, iPads, and Sony tablets have added features to increase the consumers' productiveness.
nVidia is proven to be one of the best, if not the best, processor-makers in the industry. Their Tegra 4 has 4 cores, just like Qualcomm, but the Tegra 4, if I'm not mistaken, has 5th core that does special tasks. Like the Apple A7, it is dual core, with 3rd sensor processor.
Back to the topic, Shield Tablet maybe the most powerful tablet as of now. It's not generally popular unlike Samsung and Apple, both of which spends billions of dollars in marketing alone.