I find the experience rather freeing, personally, because I tend to do most of my GMing off the cuff. There's a fantastic amount of inspiration from every corner of the world. If you like more structure, the cities of the Steadfast have somewhat more unifying tech (often culled from the same source) and larger organizations with defined goals.
There's an infinite amount of fascination, because if I decide that the Clock of Kala is an actual clock that starts up at certain dates of celestial significance in one campaign, in the next I can say it was a trap for some ancient destructive force and that the Shear accidentally broke the lock on its cage, or in the next one I can say that whatever made the Shear in the Clock of Kala was just a trial run of some ancient weapon or tool and is now being activated against past targets of dire significance... And the players cannot even have meta knowledge about it, because while they might know what the Clock of Kala looks like, what it IS is my determination and mine alone. They can't figure it out just by reading its entry in the book.
I find it no more difficult to come up with plots for Numenera than I do for your typical D&D dungeon crawl, city adventure, or wilderness exploration where you have to rescue the princess from the tower (or the ultraterrestrial from an interdimensional prison), uncover the grand vizier's evil plan (which is a bargain made with the royal household artificial intelligence to free its nanobot children in exchange for killing the king), or gather a rare herb to cure the elder druid (or convince a recently-awakened regeneration pod to share its bounty with "foreign organics"). It's just now the players cannot "look behind the curtain" so easily, either from the text of the game books themselves, or the books, movies, and other media that draw from more popular fantasy and sci-fi tropes. The weirdness of Numenera gives you an element of surprise that keeps players on their toes, in my experience