It's not as hard as many posts would lead you to believe (I've read many where people just rage quit the game at certain points), but it has an excellent difficulty. There are some tricky platforming sections later on that demand fast reflexes and a good handle of the controls, as well as a 'puzzle' element where you have to figure out how to navigate the area. Also some fights and boss fights are pretty tough, but are never unfair in the slightest. Basically as long as you have a handle on the controls and mechanics, it will never be too hard or too easy. There are some side challenge things that are pretty difficult though. It's a great game though, stick with it and you will be pleasantly surprised by the challenge I think, as it absolutely gets tougher.
On the topic of SOTN, I've only tooled around with it for a little bit, but I've actually sort of gotten myself stuck. I think it's right after the first proper boss fight of the flying bird guy who drops the spear dinosaur, and I can't seem to survive long enough to make it to the next checkpoint after it. The music is great though, and the combat is fairly fun. But all in all it seems like a much more simplified version of Guacameele, even the platforming seems like it's just hopping around little platforms in a castle whose architecture makes literally no sense. Hopefully I can get past this part though, maybe I'll like it more once I've gotten further into it.