For one, I was disappointed with the supposed difficulty or profundity of the course. Just like miles above, my fellow attendees, the teacher, the guru, and the friend who recommended the course to me in the first place, all described the experience in very dramatic terms (hell, heaven, profound impact, etc, etc). In reality, for 10 days, you don't do anything but sit in a dimly lit room for hours on end and concentrate on your breathing and other sensations. In between, you eat and sleep. That is all. Personally, I haven't found it especially challenging to shut up and focus for a few days. I also can't say that several days of highly-enhanced perception that followed the course had any profound long-term effect on my life. It was nice, but not more than that. (Those of you who do yoga probably know what I am talking about - those couple hours of feeling balanced, clear-headed and less "ADD" immediately following a yoga class).
Also, I felt that the course was misrepresented. What attracted me to this particular form of meditation was the promise of a 100% non-religious, 100% evidence-based practice. The website, the live teacher and the videotaped guru/founder S.N. Goenka stressed over and over the importance of personally and physically experiencing any insights. On the first day, we were told that we must simply observe any sensations that come with the breathing and not intellectualize the experience or give it any meaning other than what is. However the very next day, we were fed a whole bunch of hooey about the life of Buddha Gautama and the attendant reincarnation theory. The Buddha's tale was presented as a true story, and the reincarnation cycle was presented as the imperative to practice Vipassana mediation. The gist of it was, if you are good (i.e. you practice) you will eventually graduate to an enlightened status, but if you are bad (you don't practice, or waste your time with other meditation methods that may mean well but are silly because they focus on chanting or other false techniques) you will continue to suffer here on Earth. I really didn't appreciate the disconnect between the non-sectarian promise of the course and the reality of what the guru was telling us from his videotape each evening.
To be fair, I will add that the brainwashing is of spiritual rather than commercial nature and the course organizers do not want anything from you other than to "get" it. I would say that if you can set aside the negative aspects I mentioned above and you have 10 days to spare, it's a great way to reset your focus. Just don't buy it when they tell you that something incredible happens on the sixth day. They re-iterate over and over during the first 5 days that you must stick it out and something profound will happen on Day Six, but it's the same thing every day - meditate, eat, sleep, meditate, eat, sleep.