What exactly is PRaT???

Good summary Gregm. The irony is that the the LP12 of the mid eighties had dreadful micro timing stability due to the movement of the subchassis/armboard relative to the platter. Linn's mantra was pitch and rhythm. I have a feeing it was the journalists at The Flat Response magazine that converted that into PRaT.

Bias a tube amp a little low in mA and you’ll hear sluggishness that is moving toward lower prat. 
 

while I like OP’s binary approach to how a system sounds (does it right or not), I think if you go back and relisten to what’s working and what’s not, you’ll find sometimes a system has great soundstage, imaging, etc But it’s still falling into the not doing it for you bucket. That might be a lack of prat. 
 

some folks just here things differently—like OP’s view on Klipsch.  To me, they can be good rock speakers but some Klipsch offerings can convey delicate pieces and dynamics in a way that makes others sound brutish. Yet, OP hears “in your face”.

one may never hear things and that’s a blessing or maybe a curse.   Not sure.  

@gregm Ivor Tiefenbrun was a brilliant marketer for sure. He took the essence of British Hi-Fi and translated that into words to get awareness in the US market. I think Linn's products back in the 70s and 80s were not so different from other audio components from the UK, but the main difference was that Ivor created a "philosophy" to describe what that British Hi-Fi sound did well.

He got what many engineers miss about marketing. It's about trying to sell your strengths, not covering up all weaknesses.

My perception at the time when the phrase first appeared was that it was an anti spec approach to SQ evaluation.

Back then perceived quality of all audio components was based on spec analysis. 

@richardbrand

Of course, the actual music does not really slow down, nor change in pitch, nor timing (unless stylus drag actually slows a turntable down!)..

But our perception of when the beat starts is affected by the arrival pattern in time of the first transients of a note. If the leading edge is sharp, not smeared in time, your brain will snap into recognising the start of something special. I am suggesting microseconds here! Get this right, and you’ll likely find your foot tapping ...

Seems plausible.

@calvinandhobbes

The type of music you’re listening to matters in term of whether PRaT is relevant.

 

Perhaps I simply don’t understand how you are defining PRaT or perhaps it’s the fact that how rhythms are presented by a system is vital to my engagement as a listener, but either way, I’m having difficulty grasping how any genre wouldn’t benefit from a system that presents PRaT well. . . unless one is solely listening to ambient music that "hovers" in space.