Late to the party, but I've owned my DigiQ-II for quite some time now. Bought it originally for the POSK, which definitely needed it for long overnight cooks. The KK is a lot more stable, but as others have said, I like the security blanket of using it on long cooks. Didn't need/want the WiFi version or one with a smartphone app.
One bit of advice, FWIW - the Guru's have a damper on the outlet of the fan that is a good thing to have on a windy day. The wind blowing across the top hat will draw air into the KK even if the fan isn't running and will cause your temps to continue to go up. Once your temperature edges above the setpoint, the Guru (or any other device) can't bring the temperature back down - it just stops running the fan. So, having the damper to choke down on the airflow on windy days comes in quite handy.