Hello z3nk0,
it helps to have some experience with photoshop, but its not essential. it also helps to have some notions of drawing, but the most important, which is shading, I explain in detail, so you are safe there!
some of the students are posting their artwork on twitter and on the discussion boards, the artwork is really good. Some have even taken the exercise sprites and made them into something totally different, which is awesome.
I think udemy gives you a 5 minute test for each course, so maybe you can try that and see how hard it feels to you.
BUT, and since I've just reached 400 students, and to celebrate,I made this promotion that you can get the course 20 dollars.
its a great chance to learn pixel art and use it on your video games.
the promotion is only available till the end of March, so if you are considering enrolling, use this opportunity!
enroll here:
http://goo.gl/Ib4yRgEnjoy!
Marco