They work, but like any tool, it only performs as well as the training done by the user allows it to work.
With training it works well. Without training, it gets cluttered and confusing really quick. It just depends on how much time you can, and will, spend training yourself to use it. Some don't like the additional work it takes to use it effectively (or they already have an effective process that negates the need for the T-3), and so, don't like or prefer it.
I have a Mk5 with it. <shrug> It WADs (works as designed), but no better than also learning the MPH of your gun, and learning to calculate that in your head on the fly. The T3 is just that; a different way to establish a base number for wind calls, and then apply it on the fly.
JMTCW...