To tell you the truth, I fell on the 'hindu squats are bad for you' bandwagon for a long while. Having guys like Scott Sonnen go along with condemning them helped that I guess.
But mostly, it was just that I didn't like Matt Furey and the way he presented them.
I don't think they're guaranteed to injure you, and that doing them probably is good and does help 'condition' you to some degree.
By that same thing though, Furey is a hypocrite because when he does one-legged squats, he does them in the traditional flat-footed 'pistol' method. Whereas if you look at guys like Ross Enamait, he doesn't call it 'hindu' anything, and he just does a 1-legged pistol and goes "or you can squat on one leg" and none of this nonsense like "the magical exercise" or "blowtorches fat" or any other adveritsing slogans.
Basically, they're a neat exercise, but just one of a plethora, it's hard to see why it should be a form of a program. I would think doing a mix of heels on the ground normal sitting squats and hindu squats would be more valuable. Normal squats probably emphasize the posterior chain more since it seems like a lot more hip flexion goes on, and also you tend to round your back to keep forward so you don't fall, because with heels on the ground sometimes it feels like you're falling back and you really need to pull yourself forward.
Hindus are a little more calf, but not really... and a lot of quad and stuff.
I think they can injure you if you do them recklessly or jump into them. Part of the reason I stayed biased for so long was I did 500 off the bad (despite falling down several times near the end) and then I couldn't work the next couple days due to the DOMS (I was scared I injured something) and almost got fired because of it. So basically, much like anything, you ease into it and don't overdo it just to prove how easy something is.
Another thing is, we do weighted flat-foot squats, and they're much more stable and suited for weighted exercise. Much like doing 1-legged squats or going on a wobble-board or whatever, hindus are more suited for proprioception training. You could do them a little weighted though over time, so long as you were using much higher weights with your flat-foot squat. If you can squat say, a 200lb barbell, then doing hindus holding a 20lb medicine ball or wearing and 84lb weighted vest probably wouldn't be horrible, so long as you also worked up to that gradually too.
The thing about hindus is... wrestling have to learn to shuffle around. I've read a book on acrobatics and tumbling and clowning where you basically train from that bottom position to go down onto your knees and back up again, and one method of japanese martial arts involves walkined in a kneeling position where you continuinely switch which knee is touching the ground as you shuffle forward. That kind of stuff is just as valuable I think, and probably more useful.
Bodyweight calisthenics are fine endurance work, but probably not the most focused kind. Measuring heart rate or running/cycling speed over a set period of time is the best kind of cardio. Calisthenics are just sort of a supplemental thing, or you can add them in road work to add to the strain while giving certain other things a rest.
For pure strength, adding resistance is important. This is one thing that's good about Kurz is that he recognizes the important of progressive resistance training. Body-weight only advocates are just ridiculous. Even if Furey's hyping stretch bands now, it's still really stupid and too late for people to forget the stuff he spouted about "musclebound" and "weights injure you" ridiculousless.
With squats, yeah, just adding a barbell doesn't simulate what humans usually go through. We often bear weight on only one leg at a time, and often with a straight leg. This means that one-legged training, and training that does not load the torso would best suit things like running or kicking. But at the same time, we are load-bearing organisms, so adding a little weight is fine, especially since we DO carry things, and sometimes even on our backs.
One-legged squats are great, squatting with concentric-increasing resistance curves (bands, chains, nautilus/bowflex equipment) is good, and squats that stress the legs without stressing anything above the hips are good (like weighted belt, dip belt squats) and stuff like uphill climbing/sled dragging.
By that same bit, I think if used properly, the leg press is good since it doesn't load the torso like squats do, even if it isn't a freeweight exercise that recruits stabilizers that much. You can do them one-legged too. It's probably the only safe way to do a pressing motion with both legs totally adducted (pressed together) since squatting like that is too risky, and it's much easy to do calf raises that way.