I have one mounted on the back of my Slayer Propel 10 seat and I love it. Inexpensive, as kayak accessories go, A Velcro seal at the top to secure objects put in it, really well made, accessible. It also appears to be one of those accessories that would fit a wide variety of seat backs.
I keep my tackle under my seat in two Plano 3600s using an under-seat storage option from Native. I haven't seen an under-seat option from Tackle Webs but if they make one in the future, I'd likely pick it over the Native product.
Inside the Tackle Web, I usually keep my sunglasses/glasses, sunscreen, maybe a small towel or a sponge . . . anything that I might use often but don't really want to turn around and scrounge in my milk crate for. I use the milk crate for my anchor assembly, lunch, water, other things I don't reach for as often.
One other thing: I used four of the bungee cords to attach the Tackle Web to each corner of the back of my seat. This may be specific to a Propel 10 seat, but I only needed 4. My kit came with 6 and they can be attached, too, to the back of my seat forming bungee loops to attach things to as tie down anchors.
Anyway, a really solid 10 rating. So often with kayak accessories, they are just okay but not great and always pricey. Carts come to mind . . . so many are cheaply made, yet expensive and designed with flaws.
Nice to find an accessory that leaves you feeling like you purchased a true value once in a blue moon.