By ~15% compared to >160% for Bulldozer.
And this is day zero before any applications have been optimized for the new microarchitecture, compared with Core which everything has been targeting for more than a decade.
They did good.
Would you do it if you had the choice between that or adding new money making features/fixing bugs?
Of course I would, because people are going to benchmark my software against my competitor's software and choose the one that runs faster on their hardware.
Especially if my software is a compiler and people are benchmarking the programs it produces against other compilers, which is where most of the optimizing actually happens these days.
As for the priorities of the compiler devs, I think it will get some love.
Besides, if your application is one where performance is a serious issue, then you are going to spend some time optimizing rather than adding features. For some applications, performance is a feature.