We will mainly focus on the dual-core processors and what they'll do for mobile systems. For a detailed rundown on the quad-core processors, check out our hands-on look.
Haswell is Intel's code name for the fourth generation of Core i-series processors, those ubiquitous chips found in nearly every laptop, desktop, and (Windows) tablet out there. The last generation, code-named "Ivy Bridge," was released mid-2012. The newest CPUs come in a variety of types: desktop-based quad-core processors, dual-core mainstream processors, lower-power longer-battery-life ultrabook processors, and processors aimed specifically at tablets.
You can get PCs with the higher-end quad-core processors first, but these are expensive, high-performance machines. Intel leads with the high end first, then releases the middle-range processors (in other words, the ones you'd want to buy) later on. A number of systems will pop up over the next few months, but by the fall most PCs should have them -- not all, though.
You'll never see "Haswell" anywhere on an actual product box, so strike that from your memory. They're still all Core i3, i5, and i7 processors, ranging from i3 (slowest) to i7 (fastest), with a variety of speeds and types for each. Just make sure the first number after the "i7" or "i5" is a 4, as in "Core i7-4650U." If it were an older third-gen processor, that four-digit number would start with a 3. More specifically, Intel has also created four classes of mobile processor based on PC type: "H" for high-end quad-core processors, "M" for mainstream quad-core and dual-core laptops and some desktops, "U" for lower-power ultrabooks, and "Y" for super-low-power tablets and detachable hybrids. It's confusing, but that's why we compare different PCs with benchmark tests.
New dual core processors are faster than last year's processors, the real impact will be giving ultrabooks and tablets better battery life and graphics performance. We haven't tested any of the newer dual-core processors yet, but Intel claims up to 3 hours better battery life for ultrabooks, and significantly better graphics for gaming over last year's equivalent third-gen Ivy Bridge processors.
Intel's newest integrated graphics should handle gaming, video encoding, and graphics-based tasks a lot better. Keep in mind, though, that different fourth-gen processors have different levels of Intel graphics. The Iris-level pro graphics aren't the same as what you'll be getting on a new Haswell tablet. Last year's Intel HD4000 integrated graphics were a nice bump up from the previous HD3000 graphics, but weren't as good as higher-end dedicated graphics options from Nvidia and AMD.
Wi-Di 4.1 is built into new Haswell processors. Wi-Di, Intel's wireless display technology for beaming video and sound to a TV or monitor, has been around for several years, but the latest version features less lag and a new touch-friendly interface for touch PCs. Of course, you'll still need to find a TV or plug-in adapter that's compatible with Wi-Di. Also, according to Intel, fourth-gen Haswell ultrabooks will have faster wake-from-sleep times (under 3 seconds) and perceptual computing interfaces built in, using the Webcam and microphone to record gestures and voice. How those will work remains to be fully seen, but were teased at CES.
Intel is making touch screens a requirement on all fourth-gen Intel Core i-series ultrabooks. Now, that doesn't mean all slim laptops will be touch-enabled; it just means that those that don't won't be called "ultrabooks." Expect the majority to be touch, especially as prices drop, but a good handful of PCs will likely stick around without any touch at all.
If you're considering an ultrabook or tablet and want really good battery life or graphics, then yes, those gains could be worth waiting for. For mainstream laptops, that remains to be seen. You're always better off getting newer hardware, but the difference in a larger laptop might not be as dramatic. As always, you could try buying a laptop with a last-gen Intel processor online and see if there are any discounts.
Prices of these systems will vary, of course, but Intel says two-in-ones, meaning those ultrabook/tablet convertibles, sporting a fourth-gen dual-core Haswell processor could cost as little as $399 by the holidays. Most PCs will probably cost the equivalent of what the previous systems did.