Ahhh myst. I played the original, Riven, Exile, and Revelation all without any online hints or outside assitance. Sometimes it would take several days or a week (or more) to figure out a puzzle, but I was nothing if not persistent.
I liked how it wasn't always just about solving a puzzle ... often the harder part was just trying to figure out what the puzzle was that needed to be solved, especially true in Riven.
I also remember one pixel hunt in Riven that probably stumped me for weeks ... some microscopic button on top of an idol. But logically, it makes sense to hide a button that reveals a secret passage ... right?
So it wasn't unrealistic or unfair at all really ... it just required patience and attention to detail.
An important thing to note is that you have to be in the mood to play myst to enjoy myst. If you sit down with even the slightest tendency towards impatience, you'll start to get into trouble and hit walls that will require extensive backtracking. If you sit down and fire up Riven, when you're really in the mood for Serious Sam, expect to be unhappy
But sometimes, when I'm all FPSed out, I want a slow paced, absorbing experience that lets me take a step back and think and explore a fantastic world. Myst is for those times.