There are not widespread issues with KitKat. A vocal minority have a few things they don't like. There are no major bugs and there are a few nice improvements. You really should just update. As far as seeing threads about the negatives of the update: How many people are going to come onto a forum and start a thread to say, "I just updtated to KitKat and I didn't have any problems"? Not many, especially compated to the number of people who will post about the problems they had. Even though there are far more threads complaining about the update than praising it or saying it was no big deal, you should understand that people who don't like it or are having problems with it are an extreme minority of Moto X users.
Note, there has only been one person in this thread that didn't like the update, and that wasn't because it was buggy, but because "There are plenty of so called improvements that are not improvements at all. Everything works just fine but certain aspects of the UI no longer have that simple, no frills aspect that was the reason I wanted a Moto X." And, frankly, I can only think of two three (forgot about the dialer until I saw another thread about it) UI elements that changed in KitKat; Holo Blue clock/battery/signal/etc. is now white,an improved dialer and the menu bar and notification bar are translucent on the home screen. I'm not sure which of those ruined the UI of this posters phone, but I like both (though I have long complained I didn't like Holo Blue).