Keep in mind that many of the courses are listed for prices significantly higher than the price they actually sell for. As I explained in an earlier post, you do not have to opt in to all the sales that they publish and you can stick with your posted price. The problem with that is your sales would be almost non-existent when you are competing with material that is on the same subject as your material and selling for 90 to 95% less.
I think in many ways they have protested the practice, they do not update the material, getting accurate answers to questions is next to impossible, and something I have noticed over the last year is that it seems that one or two guys will go through the registration process for Udemy and then farm out the development of the material overseas. So you get this really nice introduction video, high quality video and audio, and when you see the actual material, different person, low quality audio, hard to understand, etc. I have noticed a couple of my college students complaining about that when they ordered some classes.
I am pretty certain that those practices have impacted the quality of the instructors they have on the site. Like most other things, they just look for instructors in other places as cheaply as possible. That is the way of the world now.
The biggest turn off for me was ownership of the material. Once it is on their site, they control it and there is no way that I would do that.