In terms of belay krabs, this is by far the best I have ever used. The belay master has many of uses mainly to stop cross loading but also allows a smooth operation of the rope. However, for me personally I find two very positive impacts it has.
1 - when taking a group climbing I always do the krab squeeze test to ensure the krab is screwed up correctly. This means doing a physical check each time the threesome is ready to climb. Although this is added safety, it can become quite tedious. However the belay master 11 will not close unless the screwgate is correctly tightened, allowing me to do a visual check.
2 - due to the nature of lead climbing, there is often a healthy amount of slack in the rope. Because of this the belay device becomes more relaxed and often causes a cross loading accident. Previously I have constantly taken my eye of the climber to ensure I am not cross loading. However, once again thanks to DMM I am able to keep an eye on my climber with the comfort of knowing that cross loading will not occur.