CPUs have not gotten significantly faster in the last couple years, especially at the high end. Back in Q1 2010 I got an Intel Core i7 980X which benchmarked at 8911 according to http://www.cpubenchmark.net/cpu.php?cpu=Intel+Core+i7+X+980+... Now in Q2 2013 (3 years later) the very top of the line processor available, an Intel Xeon E5-2690 v2, is only twice as fast at 16164: http://www.cpubenchmark.net/cpu.php?cpu=In…
Depending on what you're doing with CPUs there have been improvements, even at the high end between Nehalem and Haswell (on the Intel side). Anandtech's data shows a nearly 2x improvement between those generations for certain tasks.
But the reality is that for other tasks (e.g. the winrar compression benchmark) the speedup is minimal compared to previous years (see Haswell vs Prescott). In many cases where there is a speedup, performance is already so good that you wouldn't notice.
It's pretty crazy to see that in the consumer world, not even games are demanding so much performance from our CPUs.