The price - For under $700, there's simply no competing with the Seiki Digital SE39UY04. Providing a 3840x2160 panel for this price is unbeatable right now, and even with any downsides to it, it's a steal at under $700.
The quality - Once it's configured, it looks beautiful. The colors pop, the text is crisp; it almost smells perfect, too. There's no fluff included, no "smart" apps (something I find useless on a TV); it's just a bare display. It's perfect for your desk.
4K is the future - There's no denying it: 4K is the future. Once high resolution displays get to 4K @ 60FPS for under $1500, they'll start selling in better numbers. Display connectivity technology (such as DisplayPort) is catching up, slowly.
Some issues on certain PCs - I had issues with the panel on my new Intel NUC, so you'll have to be careful of what you're plugging it into. Any of the new AMD or NVIDIA video cards should have no problems at all.
Downscaling - If this panel could do better downscaling to 1080p at 60FPS, it would be just too dominant. This is one poor aspect of the panel: Every resolution, but 3840x2160, looks terrible. It's not too bad in games, if you're sitting further away, but at arm's reach, it's horrible.
Seiki Digital isn't about to become the next Samsung in the world of TVs, but it is disrupting an otherwise controlled space. The big boys are charging multitudes more, but not really delivering all that much more in terms of what you're getting out of the box.
Sure, a big brand set might aesthetically look better, and might win more praise for its better image quality, but that's what you get when you pay 3x, 4x, or even 6x more than what this panel costs. ASUS is charging over $3000 for its 31.5-inch 4K panel, but do we get the same increase in quality (picture quality, response time, etc) as we do in price? No, no we don't.
Sure, we get 60Hz, but it's not even a real implementation of 60Hz; not yet anyway. We are still away from 'quality' 4K desktop monitors, but I think 2014 will be the year of desktop 4K.