I like the idea in principle. It adds variety to the game world, and forces me to actually scan the area ahead, rather than just plowing through and dominating every enemy I see. Also addresses that old question of why enemies are always ~5 levels of me as I progress through the game.

That being said...I really didn't like its implementation in Xenoblade Chronicles X. I had some exploration sessions ruined after coming into an enemy's range and having them chase me for 10 minutes, since apparently these monsters have nothing better to do. It was so bad that I eventually just let myself die when I got into those situations...didn't care enough to spend my whole gaming time running away. 

It gives player an idea of the power they will some day possess, and help build a more realistic world.
I like them.

Haha. I think You just gave me an idea for a troll boss. It has a super weak attack of 1 hit point, but it just keeps on healing, and dishing out status effects to your party. It looks impossible to beat, and there's an autosave just before you fight it that overrides all your other saves, but once you reach your 50th turn in battle, one of your characters breaks the fourth wall, and shatters the HP bar with a mallet. Then your character rambles on chastizing the developer. 

Lol, I just might use that in my Dragon Quest fan game!