The fact that there are specialized PC vendors to build PCs tested for audio use sort of suggests the "state" of things - lots of testing, measuring and tweaking involved that can be unexpected coming from a dedicated instrument. Buy a midi keyboard and some plugs and expect things to just work? Probably the even more common scenario is DJ's, they use midi controllers as well and this trend was obvious over 15 years ago when people started DJ'ing with mp3's on the PC. Yeah.. lots of DPC testing going around in those DJ forums as well.
On one hand I'd like to see the "state" improved but I'm sure there's a ton of vendors pleased with status quo.