A lot of us have done the high rep thing with sets of 50 to 100 to even 300 with some exercises thinking we were building endurance and strength. Maybe, but I also racked up joint irritation and pain from doing this. In retrospect I'd have been doing better doing circuits of different exercises and keeping the reps under 25. Here is an example of a leg workout this morning:
Five Circuits
DVR Leg Extension from PYTP -10 reps each side
DVR Leg Curl from PYTP - 10 reps each side
Step-ups on a chair - 12 reps each side
Iron Mikes (Lunges) - 10 each side
Hip/Hamstring/Lower Back DSR - 10 reps
One Leg Calf Raises - 15 reps each side
I've been doing this for several workouts and it provides a good balance of strength, coordination, balance, flexibility and to a certain degree - size in the right places. Any other words, no one set of muscles becomes overdeveloped.
When you stick to one exercise doing 100's of reps you tend to overbuild the areas that create the least resistance, so you can do more repetitions. In other words, taking a Hindu Squat - you tend to overbuild the glutes, the hips, and the outer sweep of the thigh - depending on your genetics. This also can inhibit the range of motion for other muscles. I know personally, doing the Hindu Squats in high numbers inhibited my stride for running.
Think about your own personal experiences with high repetitions, and I am not discounting that some may have had positive results. I think though, many of us have had issues and would be better off working sets with moderate repetitions as opposed to one all out high set.
I would say 25 reps and below is a good range depending on the exercise. I'd rather make an exercise harder by using tension or a harder variation. My personal opinion would be anything above 25 reps with calisthenics and weights is a waste of time. I believe self resistance, VRT and cables can be done with higher reps. They have less impact on the joints. I think the higher reps with these are a good change up plus a nice pump.
That being said, I prefer to switch up my reps and sets. It all depends on what I'm doing.The rep ranges that I use now are 5-8, 10-12 or 15-20. For me switching up the rep range keeps boredom at bay and applies a differant feel to my training.
In my workout, I stick to 4-6 sets and 10-15 reps in each set. I try to use high levels of voluntary muscle tension that do not allow more reps. No high numbers! It is a good choice for my joints.