Long story short, using the Core i5 / Core i7 "Sandy Bridge" CPUs under Linux is possible. If using a P67 motherboard with a discrete graphics card, Ubuntu 10.10 or any other modern distribution should work just fine. If you are after Intel's new integrated graphics, not only do you need to be using a modern distribution for now, but also you need to be building your own driver (or obtaining the packages from a repository) so that you are on at least the Linux 2.6.37 kernel, Mesa 7.10, and xf86-video-intel 2.14.0. When doing so, it should be quite a pleasant experience unless you find yourself with the same motherboard issue that I have been reporting.
As of the time of publishing this article, the exact cause of the Sandy Bridge Linux graphics motherboard issue is not known let alone resolved. The problem though has been reproduced independently on the ASUS P8H67-M PRO motherboard, so I would recommend avoiding that motherboard when shopping. However, without knowing the cause of this problem, it's unknown what other motherboards may be facing the same issue -- especially as ASUS has many P8PH67 motherboards on the market and they are not some obscure Taiwanese vendor producing shoddy products. The simple test that I do, which is always reproducible for this issue on my P8H67-M PRO setup, is simply running phoronix-test-suite benchmark build-linux-kernel, which will build the Linux kernel three times (or more, depending upon variation in the results) with the compiler using twice the number of jobs as the number of CPU threads. For the Intel Core i5 2500K it means building the Linux kernel with eight jobs. Within a few minutes of commencing the build on the first or second kernel, if the problem is present, the system will lock-up and the screen will become corrupted in a checkerboard-like tiling pattern.
While it's been a headache dealing with the Sandy Bridge Linux issues on the ASUS motherboard, during the short time thus far using the new Intel motherboard with the Core i5 2500K, the experience has been extremely pleasant. On the software side, it has been tested with Ubuntu 10.10 atop the latest Linux 2.6.38 kernel (for the tests in this article, using a kernel build from Git on 2011-02-07), Mesa 7.11-devel, and xf86-video-intel 2.14.0 as the central graphics components. You also need to be using an updated/modified version of Compiz to support compositing on Sandy Bridge as the SNB PCI IDs are blacklisted in the version found with Ubuntu 10.10. This is similar to what will be found in Ubuntu 11.04, Fedora 15, and other distributions coming out in the next few months to provide a pleasant "out of the box" experience, sans any motherboard issues.