Sandy Bridge E is a benchmark crushing series of processors. You're talking about 6 real cores, with HT and serious overclocking potential. The die is titanic by comparison to a standard Sandy Bridge die, and it doesn't even include an IGPU! In every performance metric, Sandy Bridge E outperforms its predecessor, not to mention the absolute hash it makes of AMD's offerings.
Unfortunately, Sandy Bridge E's performance is matched, then exceeded, by the price of the platform as a whole. The cheapest Sandy Bridge E processor is as much or more expensive than the top of the standard SB heap, and if you're buying into Sandy Bridge E for a glorified 2700K, you're doing it entirely wrong. Then you have to consider the price of a solid motherboard, the cheapest of which will likely start in the $200 range. When you consider the fact that the performance offered by a 2600K/2700K was already well in excess of what is necessary for gaming and general computing usage, it becomes incredibly difficult to justify Sandy Bridge E as a computing platform for the general consumer.
You would want Sandy Bridge E if you are, say, starting your own space program, or plotting to take over the world. You might use it as the centerpiece of a device designed to use mathematical calculations to warp the very fabric of reality. I'm not entirely convinced it couldn't be used to resurrect the dead.
All of that doesn't mean that super-villains are the only people who could use the kind of horsepower that you get out of a Sandy Bridge E based PC. Professionals with video editing, 3D rendering, and/or CAD needs will find this kind of number-crunching ability compelling, as will those involved in high-end computing/distributed computing projects, like Folding@Home. Still, those with the need for that much processing power are decidedly in the minority, and those outside that minority who buy into the platform are undoubtedly enthusiasts with deep wallets and misplaced priorities. Normal people with reasonable budgets and no deep-seated need to compensate for something will be perfectly happy on the LGA1155 platform.