There is a lot of negativity here about this update, but 2 things to keep in mind:
1) As Intel announced, these chips aren't available for another 6-8 weeks. The first PCs shipping with them will be in August. Apple couldn't wait that long, they needed to upgrade to the new Force Touch trackpad.
2) Broadwell is an insignificant upgrade. Benchmarks show a 10-15% increase in actual speed, and the Iris Pro 6200 is about 10% faster.
I am willing to bet Apple tested Broadwell and Skylake, and decided to skip Broadwell for now in lieu of launching Skylake end of this year or early 2016.
I personally think this was a smart decision on their part, and I purchased the maxed out 15" a week ago. I'm happy with it, it's a nice upgrade in every regard. Screaming fast SSD, a quad core Haswell I haven't been able to bog down even with video editing, and a new dGPU that makes me proud of AMD (I've been an Nvidia fan for most of my life, but this thing is solid).
Am I disappointed Broadwell is coming out in 6 weeks and I bought a Haswell? No... well, maybe a li...who am I kidding? DAMN YOU APPLE!!!