Before getting too excited about Broadwell desktop CPUs, the Core M Broadwell-Y chips are just intended for tablets and ultrabooks that will be shipping this calendar year. As expected, those after Broadwell CPUs for desktops and other lines will end up waiting into H1'2015 for the Haswell successor to finally appear on desktop systems (Broadwell-H). Broadwell-Y is the line of SoCs with sub-5 Watt TDPs shipping under the Core-M branding.
The 14nm Core M Broadwell-Y chips should come in at about half the power use of similarly equipped Haswell chips thanks to the die shrink and allow the chip to be used in fanless mobile designs less than 9mm thick. Besides consuming less power and taking up less PCB real estate, their graphics are much better and there's other additions over Haswell like VP8 video decoding and new instruction set extensions.
Intel is currently promoting to its partners a 7.2mm-thick convertible tablet based on Broadwell-Y codenamed "Llama Mountain", but the only downside is that the Llama is packing Windows 8.1 although Intel remains committed to Android x86 in the mobile space.
In terms of the Linux support for Broadwell, as we've been reporting for months it's nearly spot-on and ready to shine. There's still some graphics features being worked on but overall using the latest Linux code right now along with other Git code of crucial components like Mesa should be good enough for the initial roll-out support. Performance optimizations and other features to tackle are expected to come over the next few Linux/Mesa release cycles while the Intel Open-Source Technology Center crew has already started working on Skylake driver support, which is Broadwell's successor.