well, new F3 revision cpu's (with 2x1mb L2) are hitting 3.2-3.4 on good air... but that's about the max for the K8 architecture, even the brisbanes
problem with most, if not all current K8 cpu's, is the cold bug.... meaning, if you deap freeze (i.e., phase/ln2/chilled water), you can only go so low on the temps before the cpu starts bugging out, to the extent that even the FX-62's unlocked multi's don't help very much. And considering most current cpu's are overclocking to 2.8-3.0 on air, there's really no need for expensive cooling, or expensive cpu's for that matter...
let's hope the split power planes on the K10 architecture helps cure that cold bug....