It's abouut as rigorously defined as most things in psychology and about as easy to replicate in a lab as most things in psychology. It labels repression of emotions as a bad thing, but you can find a half dozen studies showing people who ignore traumatic events have a faster and healthier recovery than those that don't - and then turn around and find a half dozen studies showing the opposite.

Its main value is as a political tool to try to change people's behavior you disagree with, simply because you don't like it. When it stops being useful, it will be dropped for the next fad.