I've only had KK for a day, but I notice that it takes a few seconds longer to boot up after a conld start. Also notification apps (battery, outside temp, calendar, time of day, etc) take about a minute to appear -- about twice as long as with 4.3. On the other hand, my (Poetic) magnetic-wakeup case seems to now function reliably, whereas with 4.3 I needed to keep wifi "on" to wake-up when case was opened. Notifications appear instantly.
Not too big a problem (yet). I'll simply turn on N7 once in the AM and let mywake-up case do its thing during the rest of the day. Interested in seeing how this affects battery drain (less grain with KK I'm told).