Here are two Facebook posts I've written about it at different times. TL;DR - tried it, didn't like it. EDIT: I should clarify that the second one is specifically about Numenera and a few bits of it may be specific to that implementation, but most of it will apply to all the main Cypher titles.
My group and I bounced right off Cypher. The mechanics are too weird and abstruse for our tastes. It's really hard to say what any of them mean in relatable, in-character terms. A high Might (for example) seems more indicative of endurance than strength, and higher scores don't (or only very indirectly) actually make you better at anything. And, especially when you see the stats in that light, there's almost nothing to differentiate characters from one another.
I feel like Cook was trying to find a middle ground between indie storygames (which don't appeal to me or some of my players at all, though I have one or two who like them) and D&D style crunch, and unlike 13th Age - a much more successful attempt at the same goal (thanks for introducing me to that one by the way!) - ended up with the worst, rather than the best, aspects of both.
Hard pass for me.
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Not a fan.
As a GM I had a hard time translating the mechanics into anything that made sense to me and my players, and kept being put on the spot by natural 1s showing up at moments that made little narrative sense.
Players felt like there wasn't enough to differentiate their characters from one another.
I also never understood why "players roll all the dice" was supposed to be a selling point. Going in I didn't expect it to be better or worse than traditional RPG play, just different. Having actually tried it, my initial expectation was far too generous; I actively hated it. It makes me feel like a passive observer most of the time. It's also very unintuitive to most players, or at least most of my players.
The math doesn't work well and making the creature designs basically "everything on a given critter has the same difficulty except for a few explicit exceptions" puts the emphasis firmly on its worst features. A one-level difference between two creatures can be the difference between a cakewalk and a nearly insurmountable obstacle and it's very hard to gauge where that line is, and the books contain no guidelines on this topic that I was able to find. You probably could make a creature that, say, is easy to hit but packs a wallop, but the system doesn't naturally lend itself to it.
Lastly, this is more the fault of the adventure design (though the rules fail to do what good they could here), but when the game keeps telling you it's about exploration, it is, if not outright lying, at the very least displaying a profound lack of self-awareness. The books talk about this philosophy a lot but then present a system that doesn't read or play like it was designed around that philosophy at all. There's less mechanical support for exploration than there is in almost any other system I've seen. (But plenty for the sort of positioning-based tactical combat that the game explicitly says is at odds with its philosophy. It's like the system and the GMing advice were written, not only by different people, but by different people who didn't communicate much.)
And the adventures, at least the smaller-scale ones in the main books and various other sources... oh dear. They're almost completely linear, with not so much as a side passage with a treasure at the end to be found; there's nothing exploration-based about them at all. Vortex in particularly actively discourages it. It describes an environment that could lend itself to extended exploration but gives you one path to follow that LITERALLY has a glowing outline around it, and a token sidebar on what to do if the players go off the path (using, IIRC, those exact words!), that mostly amounts to "shove them back on".
And that's one of the better ones in that it at least acknowledges the possibility, if in a contemptuous sort of way, that the players will take an interest in the world around them and actually play the game the way Cook keeps hammering home that they should be playing it. Most don't even do that. To give another example, "Natural and Unnatural" from one of the mini-adventure books stops giving you any detail right at the point where anything exploration-based starts. That's the one I actually ran, but once the investigation in the town was done with I had to supply about two thirds of the adventure myself.
I went in excited to try it, and I do have to say one positive thing which is that the SETTING was a hit with my players - though even that was largely due to bits of colour I kept adding that were at most hinted at in the books. But the nuts and bolts of the mechanics and adventures are not well thought out at all and if I ever run anything else in that setting again, it won't be under those rules.
