The Zeo puts out a sleep score based on hours slept, the amount of time in REM and Deep sleep and the number and duration of waking during the night. Does this have any bearing on how you feel or perform, really? In some initial data collection, the answer is YES.
From time to time I do a home-made "Whack-A-Mole" type of measurement of response time. In this little performance game an image appears in random locations 10 times in a window and I must mouse to the image and click on it. The average time it takes between clicks is logged each time I play the game.
If I do a chart of my Zeo Sleep Score vs. my response time it looks like this:
You can see when my Zeo Sleep Score is low, my response time is high (I'm slower to respond) and the reverse is true. Mathematically the correlation is low, but to our eyes we can see there is a relationship between these two independently arrived at metrics.