Unlike those monthly subscription models where you have to pay every month. With udemy, you pay for individual courses and keep them forever. This turns out to be way cheaper in the long run because I go back and look at the courses every so often which I wouldn't have been able to with monthly subscription. The monthly subscription model other online courses offer sucks because I often only want 1 course in the bundle of courses, I don't need everything else that comes with it.
Another positive: Udemy instructors are usually really responsive to questions and answer them unlike on Lynda, TreeHouse, or Youtube where instructors rarely answer questions. This is especially important for coding courses because students can run into stupid bugs that impede their learning speed.
At $10 for each course (make sure you use the coupon codes you can find online), each course is incredibly cheap. A lot of the courses are taught by experts in the field and are done really well. It has a huge range of courses by experts, from Growth Hacking, to Programming, to PPC Advertising to Drawing to Music Production.
And it's advantage over free course university institution like Coursera is that it covers a lot of topics that educational institutions simply don't cover such as Growth Hacking or learning a specific language. And those instructors at Udemy, because they are paid directly by students, tend to be more supportive and answer questions in a timely way.
Udemy needs to work on letting customer see all the reviews of a course before buying. It needs to let customers be able to sort by 1 star, 2 star, 3 star, etc reviews and see what the reviews say. Right now, the algorithm just shows the most recent 5 star reviews at the top, most of which are really shallow. Also Udemy needs to get rid of the bad reviews, like reviews from people who are only 1/4 of the way through a course.
Because anyone can create courses on Udemy, some courses are really really good, and others are really really bad and even incomplete. Therefore you have to be careful and read the reviews.
There are bad courses, and good courses on Udemy. Look at what people recommend online (offsite, ie: on reddit). And you'll know which one is good. Also make sure you use the $10 coupon codes you find online.