I was wondering if anyone could tell me from experience if it's as hard as it looks to learn.
It looks impossible. It isn't. Actually it's pretty straight-forward to solve and doesn't have a lot of difficult problems that many 3D twisty puzzles do have.
I first saw MC4D back in 2003 when I was a first-year college student. I could solve a standard Rubik's Cube then using a memorized solution but I didn't know anything about any other twisty puzzle. Of course at that time the solvers list was roughly 20 folks, all of whom I assumed were geniuses. I even wondered if they really understood what they were doing or perhaps they cheated.
I had MC4D in the back of my mind off and on for years and finally in 2009 I decided to give it a serious try. I went from "this is impossible" to "I'll never be able to understand this" to "there is a chance one day I could understand this" to "I think I'm starting to understand this" to "holy crap there is a chance I could solve this" to "I think I'm solving this" to "whoa I solved the impossible!".
Even after solving it the first time I didn't fully understand every aspect / property of it. For example you can have a 4-color corner look "inverted" where opposite colors have swapped. Almost like you've turned the piece inside-out. It took a long while for this to make sense to me.
I have an introduction video that goes very slow and tries to break the puzzle down for you:http://www.youtube.com/watch?v=Aonf34s0Bqg
And another video that describes how to find commutators for each piece (and makes use of nesting of commutators):http://www.youtube.com/watch?v=JxD8S49hbL8
My videos will take a lot of magic out of the puzzle but their goal is not to show you how to solve the puzzle. Their goal is to show you how to come up with your own method of solving the puzzle.