Wonderful for reclining, less so for sitting (and I'm short)
I bought the ZGR for back relief and it delivers. The zero gravity position eases my spine in a way nothing else in my house does, and the infinite adjustments and memory settings mean I found my sweet spot once and haven't had to hunt for it since. The heat and vibration are a nice bonus, but the recline is the reason to own this chair.
One honest caveat for my fellow short people: I'm 5'2", and as an upright sitting chair it doesn't really work for me. The seat is high enough that my feet don't reach the floor and deep enough that my knees don't reach the edge. Add the lumbar cushion and my knees are fine but my back slouches. I've made peace with this. It's a reclining chair that happens to sit up, not a sitting chair that happens to recline. If you're tall, none of this will matter. If you're not, plan on keeping your reading chair.
Would I buy it again? Yes, for exactly what it does best.