That's true, it can depend on the volunteers and the locations of the centres themselves, so it's a bit of a gamble. I've talked to a few of people who've been travelling in Asia and attended Goenka retreats after huge benders, having never meditated before, because "why not, I've got 10 days left on my visa and need to detox". Then the teachers don't speak any English in some cases. Although one person I met who had done exactly that said it was the best experience of his life, getting through it. So there's that.
I'm not condemning the retreats entirely, I just think that having a complete or even relative beginner sit a 10 day intensive vipassana retreat after basically just checking if they do drugs or take medication or not is quite a risk, and people should know that risk. My friend who had a good experience said he had no clue what he was getting into and thought it would just be a nice relaxing experience that feels good. Having presumably sat one, you'll know that's usually not the case, at least for the first 6 or 7 days, which is a long time, and can be very intense when all the advice you get is "keep going and listening to the tapes".
> It's right their in the discourses.
Also true, to be clear I think that Goenka courses are great resources for people who have sat shorter retreats before or have a long-term, stable practice. It's the "jumping in at the deep end" type stuff that happens, partially because they're free and so easy to access, partly because of the "boot camp" style image, that's risky. Many people aren't inclined to dive into early Buddhist texts and make sense of its philosophy and practice before attending a retreat for the first time.