I owned a F90BT and liked the interface and loved the customization that was possible with hacking but hated the crappy blue tooth phone connections locking up and me having to reboot the unit and it was always a LONG boot up.
So I sold it and got a Kenwood DNX8120 and liked the speed at first, button presses were really fast and boot up was more respectable but the Garmin maps drove me nuts. I couldn't ever to get street names to appear on the map EVER. Multiple emails Garmin support and they finally told me they removed that from the latest update that my unit had and I was not happy. Every screen shot had street names on the map that I had seen and my unit couldn't do it. Also BIGGIE was every time I booted up the unit it was a good 90 seconds for the Garmin to find the satellites again. Every time the unit was off for more than two hours it had to find the damn satellites, over and over again.
So back to the z110bt and I'm overall very pleased. The speed is there FINALLY. Buttons react when pressed with out delay. Boot up is quick, Navi side works good. MSN finally works really well for me with the traffic flow overlay and accidents.
So I don't know what to tell you about the new Kenwood DNX9140 but I know the 8120 needed some damn help from my point of view.