Actually it now doesn't make ANY sense that apple introduced the haswell 15" when it could have waiting just a couple of weeks.
It would be 2+ months, not a couple weeks.
I suppose Apple just didn't think they could delay the MBP update any longer.
The difference in the CPU between Haswell and Broadwell isn't much.
I think the integrated GPU is significantly improved, but if you care a lot about that you can get the MBP with the dedicated GPU and do better than Broadwell's iGPU anyway.