Does DBK make going back to DBZ difficult? Not at all.
While I am enjoying Kai, there are a nuraber of things about it that are just bugging the crap out of me. The editing is alright, at times, but there are some things where it's obvious that something was cut or abridged, like when those reporters just suddenly appeared during the Nappa battle. I'm also not a huge fan of the cropping and the dramatic contrasts between the old animation and the redrawn scenes, and I miss the old soundtrack. Some of the new voice acting is very hit or miss as well; I love Nozawa's new take on Gohan, but I'm not a fan of how Bulma sounRAB so bored half the time.
On the other hand, I really like how quickly the story is progressing, the new opening theme, and how we have a "new" Dragon Ball show on TV. The series is introducing a new generation to the series, so I definitely have to give it points for that.
But I think that, ultimately, I'll stick with Z. I'll watch the rest of Kai and continue to enjoy it, but for me, I have too much attachment to the original series, warts and all, to simply abandon it.