I think calling IE's development tools high-quality is a stretch. They got nice recently, but by far not as good as those of Chrome or even Firefox. Also it does not help that the development tools in the most recent IE are ok, I still have to maintain/debug older IEs. I think we can probably bin IE8 support, but it think only in recent IE11 the tools got good enough to not be a pain.
Not everyone agrees about IE11, but we are trying to make it better. Better emulation is one place we could do better - I'll shill a bit and call out that we do use our Uservoice [1] to prioritize feature development, so please feel free to add your votes/ideas. I can say that some of these are already in the internal builds :)
I recently had very good luck debugging an IE8 problem with IE11 in emulation mode (via Sauce Labs on my Mac, incidentally). Not sure if it works for everything, but it was by far the best experience I've had with IE.
