With Sandy Bridge, Intel made overclocking easier and more difficult at the same time. There's little headroom in the base clock, which anchors everything else on the chip. However, K-series CPUs bring fully unlocked multipliers—and a much simpler overclocking experience—to affordable price points. One can even increase the Turbo multiplier of non-K CPUs, although only by a few speed grades.
Multiplier control seems guaranteed to persist when Intel rolls out its high-end "Sandy Bridge E" processors later this year. According to VR-Zone, that platform will share a CK505 clock generator with the Ivy Bridge refresh due in 2012. The chip purportedly supports different DMI and PCI Express multipliers, allowing for a little more base-clock freedom than Sandy Bridge. VR-Zone says Sandy Bridge E CPUs will offer several base clock speed options between 100 and 250MHz. The site also claims that Ivy Bridge will be restricted to base clock speeds of 100 or 133MHz.
Motherboard makers will let you set just about any base clock you want with Sandy Bridge CPUs, but the lack of proper multipliers for things like DMI and PCIe makes it exceedingly difficult to maintain system stability with more than a few extra MHz. The presence of additional multipliers in Ivy Bridge and Sandy Bridge E CPUs looks to be a modest improvement on that front. However, outside of competitive overclocking circles, I can't help but wonder how many folks are even interested in toying with the base clock anymore. Intel has made multiplier-based overclocking cheap enough, easy enough, and smart enough that it's hard to see the point.