Still using a 775 socket Q6600! I'm desperate to upgrade but if the rumours of only a 10% improvement are true I may wait another year. In hindsight I should have bought a 4790K last year.
The Z170 is more exciting to me since it'll mean NVMe and ultra m.2 on far cheaper motherboards. With the big falls in RAM prices these are the reasons to buy. Not Intel with their expensive CPUs that are crippled by using half the silicon for integrated graphics that only a handful of HTPCs will use.