The story is familiar as you can quickly see from this quote in Phoronix's review of Haswell on Linux, "Polished Haswell support coming to an "out of the box" Linux desktop won't really be there until later in H2'2013."  However that does not mean it does not work at all, they tested several kernels and versions to find the most stable way to run Haswell and to take advantage of the internal GPU.  They successfully tested with Linux 3.10 kernel, Mesa 9.2, GCC 4.8.1, and LLVM 3.3 and found performance improvements across the board when compared to Ivy Bridge processors which could be a good reason to consider holding out on an Ivy Bridge CPU as an upgrade choice, as Intel is working to improve Haswell support and it is a much improved CPU compared to previous generations.

"This past weekend I shared the first experiences of running Intel's new Haswell CPU on Linux. While Intel Haswell is a beast and brings many new features and innovations to the new Core CPUs succeeding Ivy Bridge, there were a few shortcomings with the initial Linux support. It still appears that the Core i7 4770K is still being finicky at times for both the processor and graphics, but in this article are the first benchmarks. Up today are benchmarks of the Intel Core i7 4770K when running Ubuntu 13.04 with the Linux 3.10 kernel."

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