I just did the update. It went flawlessly. A few minor changes in the settings menu, but otherwise, it went well.
It's been out for about 4 days now. You should install the Google Experience launcher, it makes 4.4 awesome. The Apk file is easy to find just Google it and it will come right up if you haven't yet?. and turn on developer settings then turn on ART instead of Dalvik it makes app crashes a thing of the past, I have only had one app crash twice when I first started it after switching the ART then never again.