yes, that's the module i learnt about them in during college.

IMHO I think for me they're interesting because it felt like mathematically they straddle the line of being nearly impossible for me.

I could just barely do them and felt very accomplished when I could. Anything else was either impossible or easy by comparison.

assuming my maths skills are average here then most people have similar experiences with them.

What in particular did you find difficult about dealing with them?

There was something called a slerp that allowed you to get an object to rotate from on orientation to another, similar to a linear interpolation.

This was fine for some things. but if you wanted something to rotate but only in a certain way it was annoying as sometimes it would get from A to B, but go through Z during its rotation.

Getting the order or multiplications right too.

Spherical linear interpolation, slerp https://en.wikipedia.org/wiki/Slerp (which can sometimes wrap around the wrong way)

For levity, see Acts 12:4 And when he had apprehended him, he put him in prison, and delivered him to four quaternions of soldiers to keep him.