I'm not one to cheap out on the CPU, so lower IPC? nah!
On the consumer side of things, IPC has been gradually increasing, but each generation has been hotter than the last and won't overclock as much (which is only partially related to that heat) and that's why the
overall performance hasn't really changed much in the last three years.
If you only run your CPU at stock speeds though, there has been
some improvement in performance.
The LGA2011 chips are typically a generation behind, so they inherently have lower IPC than the consumer ones.
And as they add more cores with LGA 2011, the cores themselves get clocked lower.
There were a number of comparisons done around the time the new Mac Pro shipped, and an i7 Haswell would easily outperform any of the Xeons when the task only required 1-4 cores.
It's only when the software can really take advantage of those extra cores that the trade-off becomes worthwhile, and a
lot of software will only take full advantage of up to four cores.
I think there are finally improvements beyond four cores with the Creative Cloud suite, but any of the Adobe applications prior to that actually show reduced performance as you add more cores to the system for example.