Having a chip with power-saving features, and being able to actually use those features, are two different things. I suspect that if you're crunching like we do, then you won't notice quite so much of a difference.

There's bit more info here in el reg.

And a less technical overview of the Haswell chip in this BBC article

no intent to flame anyone here, just provide info. Understand, us crunchers are a special breed, what might be a break through for an average computer user, if not necessarily good for us. If this the"Haswell trend" continues, us crunchers might gravitate towards server cpus and board.

Having read a few reviews, I believe Haswell will actually be worse for a dedicated desktop cruncher. First it actually uses more energy than Ivy Bridge at 100% and runs hotter while doing it. Second, there is little gain in computing power unless the application is programmed to take advantage of Advanced Vector Extensions 2 (AVX2), which I'm sure will not happen for several years considering the time it takes a science project for go from coding to ready for us. you need a new mother board and probably power supply. It seems the idle state draws so little power, many current power supplies will shut down at idle or sleep mode.

There is little headroom for overclocking and if you do, you'll need the best cooler you can buy.

So while Haswell is great for laptops and casual users of normal apps, if I were building a dedicated cruncher today, I have to go Ivy Bridge or Sandy Bridge E

From Tom's

Haswell runs a bit hotter, takes some voltage control out of your hands, eliminates the non-K overclocks, doesn’t give enthusiasts access to the large L4 cache version, doesn’t have TSX in the K parts, and, well, requires a new motherboard, too. You’re probably wondering just where the hell the good news is for enthusiasts with Haswell....

From Xbit

...frankly speaking, this product is not that impressive at all, especially in the eyes of computer enthusiasts. We tested the top of the line desktop Haswell, Core i7-4770K, and drew a number of bitter conclusions. First, Core i7-4770K is just a little bit faster than the flagship Ivy Bridge processor. Microarchitectural improvements only provide a 5-15 % performance boost, and the clock frequency hasn’t changed at all. Second, Core i7-4770K processor turned out a significantly hotter processor than the CPUs based on previous microarchitecture. Even though Haswell allows engineering energy-efficient processors with impressively low heat dissipation, its performance-per-watt has worsened a lot when they adjusted its characteristics to meet the desktop requirements. This resulted into the third item on this list: without extreme cooling Core i7-4770K overclocks less effectively than the previous generation overclocker processors. The specific CPU sample we tested this time allows us to conclude that these processors may get overheated at 4.4-4.5 GHz clock speeds even with high-performance air coolers. And fourth: Haswell processors require new LGA 1150 platform, which doesn’t boast any unique advantages, but merely offers more USB 3.0 and SATA 6 Gbps ports. But currently this platform seems quite raw and awaits a new chipset stepping, which will fix some issues with the USB 3.0 controller.

Intel's been milking this expensive quad core processor market for quite a few years, since at least 2006. Their upper mainstream product has no more than 4 cores and 8 threads. Surely they could offer a 6 core processor for the price of a 4770k. They just don't want to because they don't have to.

Its just kind of annoying for people with important work to use those cores for. If we could still get a desktop with quite a bit more power than a laptop, more people would buy desktops. So Intel is to blame at least partly for the decline in desktop sales, along with Microsoft and Windows 8.

Sorry didn't mean to be a Debby Downer, just had to vent a bit.

They are just looking at THEIR bottom line...