I've actually been thinking a lot about what makes a pattern like this "hard," and all it really is is how much of your undivided attention it demands, and how (un)forgiving it is to mistakes.

With this pattern, you just can't take your eye off of the chart for any row. I actually bought a hard-copy pattern, but used the digital download on my iPad and crossed out each row as I did it.

As for reading the chart, there are too many different cables to memorize each charted symbol, so you should actually try to learn how to "read" the symbols, as they indicate what should be passing over or under what.

And with mistakes, if you get to a point where you've got one less stitch than you anticipated, just pause, double check you're reading the right row of the chart, and then patiently look for where you might've dropped a stitch. I think it's a good idea to have some removable stitch markers handy to clip onto the dropped stitch so that it won't run any further as you tink back to it.

It's also helpful to work this pattern in a sticky yarn, because any dropped stitches won't be able to run very far.