I have been testing the MBP with an external USB disk with OS X 10.9.1.
I have a WiFi network at home, so it's configured and connected. I also connected to the Ethernet network, and the system works fine.
** If I turn WiFi off, I get immediately a kernel panic, so the Mac freezes and need to force shutdown by pressing the power button until it does.
With this update, the system is benevolent. When I turn the Mac on again, it recovers with WiFi on, as it was before the kernel panic. Earlier versions corrupted badly the system, forcing me to start from scratch again.
I've tried to disconnect the Ethernet cable, and apparently it doesn't cause problems.
So basically, I'm using the Mac with WiFi enabled, and Ethernet plugged in. TimeMachine backups are much faster with Ethernet than on WiFi. I have a newer MBP and WiFi is much faster I barely use Ethernet for TimeMachine backups. The wireless network difference is noticeable.
I'm trying to get a kernel core dump by connecting both Macs with a FireWire cable. Normally the core dump can be done with Ethernet, but since it seems to be compromised by this problem, I'm trying FireWire IP. If I force a kernel panic I correctly get a core dump, but if the kernel panic is triggered by switching WiFi off, I don't get the core dump. I'm trying to get help on this subject.
Apple is working on this problem. A kernel core dump would be great for them to figure out where the problem is.
So be patient, we're almost there.
In my case, I can say that the latest update is pretty stable, providing I don't switch WiFi off. Although my test system was just idle when the kernel panics occur, meaning that I wasn't doing something important at the moment of the freeze, and maybe work could get lost.
OS X 10.9.1 seems to be stable providing I don't play with the WiFi connection.
I use TimeMachine for regular backups, plus SuperDuper to have a clone or snapshot on an external disk.
It's much easier to restore with SuperDuper.
Hope this helps