Pausing in the bottom position of extensor chain movements such as front squats forbids the use of the stretch reflex, thus increases intra-muscular tension, a great way to vary the strength building stimulus.
You can take a long as four seconds in the bottom position if you want to dissipate all stored elastic energy. Like any other stimulus, varying it is an added benefit. This form of work is best suited for general preparatory work. It is very valuable when training alpine skiers so their vastus medialis gets a greater overload, thus doing a better job at protecting the knees. Mixed martial artists, wrestlers, judokas and jiu-jitsukas can help prevent a host of knee injuries by regular use of pauses in bottom for squatting exercises.
This is not to say to that using the stretch reflex is bad, it is actually also very good way to train the squatting musculature.
The point of the matter is that all forms of squats improve faster when you vary their tempo on a frequent basis. These types of stretched position pauses are best suited for the training of extensors chains such as squats and presses. So for example, if your incline press has not moved up in load for ages, holding the stretched position for 4 seconds will create a very valuable form of eustress which will boost your strength levels.
If there is an exercise where pausing in the stretched position has a plateau blasting effect, it is dips. Especially when done on rings. Pausing in the bottom position in deadlifts prevents the trainee from bouncing the bar off the floor and reinforces better spine alignment which also in the long run boosts deadlift strength.
When using pauses that are so lengthy, one should restrict the reps per set to the 2 to 4 range. Because the time under tension is greater, you would do as many sets. For example 8 sets may be required when you do your dips on a 40X0 tempo, but only 5 to 6 sets are needed when the tempo is 34X0.
Also if you are going to pause that long in the stretched biomechanically disadvantageous position on presses, squats and deadlifts, you want to make sure to take an eccentric lowering of 3 to 4 seconds to set the bar properly.
The concentric range in that type of training is always done explosively.
For obvious reasons, especially in pressing exercises the use of a spotter is crucial.