I find that the results I have seen in the past when I did sacrifice form were just an illusion. Perfecting form just makes the excercise more effective, prevents injury, and generally is a greater challenge.
If you have never had joint problems, back problems, or shoulder problems, then the importance of this might be harder to understand. Injuries like these always just sneak up on you too.
Someone summarize that. I'm not going to watch 35 min of something on YouTube...
NO, I don't use perfect form for some exercises because as long as you know what not to do, you can do whatever. I think beginners need to learn perfect form.
For example, if I do a heavy squat, I won't go all the way down to parallel because I'm more likely to injure myself if I can't do it. I also wouldn't be able to lift the amount of weight I can for overhead press if I didn't vault the weights up initially--after that I can do near perfect form. Same for bench press, if you don't arch your back you lose strength, which is my goal.