Today I got a Juicedlink DT454 minimixer/AGC-disabler. I tried to get hold of a sample from Robert at Juicedlink but with no luck so I got it from another vendor.
The solution JL offered before the DT454 was the add-on DN101. You can find my article about what I thought of that one. It had some drawbacks and I addressed Robert at JL with these and I guess other users have done the same and hence he released a one-in-a-box mixer.

A thing Robert dismissed at first but finally did incorporate in the DT454 was a tone AGC defeat along with the noise method. Both of these inserts a high level signal into the right channel to trick the AGC to have their gain at the lowest. This makes for very nice sound from the left channel. Clean and without the AGC ugliness. A thing that JL didn't do was to fix the feedback from right to left channel that, with Canon cameras, makes the headphones noisy before you hit record the first time. The problem lies in the Canon cameras which somehow short circuit right-left audio input. But I think JL could have fixed this by cutting the signal from the right channel to the headphones when AGC is enabled.
One thing I commented on was how to provide for playback monitoring. Using the CX231/DN101 it was cumbersome to monitor. Now the DT454 does have two XLR inputs just like the CX231, but they have added another stereo input via a 3.5" plug that is meant to be for playback purposes. Since you have dual knobs, one for each channel, it's easy turn down the AGC (right) channel and just hear the clean channel when monitoring. How well it works I'll know during next shoot.
DT454 also has dual VU-LED meters. One for each channel. Despite only four LEDs it's helpful determine how high or low you really are. You can even have two different settings for cameras that have AGC and cameras that don't. Underneath the unit is a field of small DIP switches and I think the CX231 had a better solution to have the most used controls on the back and front of the unit instead of under where you have a tripod mounted...
Another new feature is a level knob for the headphones. The headphone amplifiers are still noisy as they are on the DN101 but at least you can turn them down. The last thing that I dislike is actually the form factor! The DT454 is wide when mounted under i.e the Canon 7D. It look kinda odd because of the shape of the camera and the DT454 somehow just goes into another direction instead fo following the lines of the camera. But then again it doesn't intrude where the battery lid is so I'll let this pass.
Doing a quick test with my AT897 shotgun mic I got clean sound and it felt good to handle.