Daisuk
10
I honestly didn’t think learning them was hard at all (except for the Octatrack, which had a few quirks too many). It depends on what you mean by “learning them”, I guess. If you want to re-create specific sounds or sound like X or Y or whatever, then it’s going to be more about learning synthesis than the Elektrons.
Just spend some time with them, is my recommendation. I have a friend who’s had some Elektrons for well over a year and still don’t know how to do very basic things with them because he hasn’t invested a bit of time in getting to know them. If you learn say the Machinedrum, you’re going to find the other ones immensely easy to use. 
But definitely read the manual. As soon as you’ve learned how to load a machine (on the machines that require this) and place some trigs with different tones, you’re good to go. From there it’s basically just a case of searching online or in the manual for features you’re struggling with.