I guess I also have a unique perspective, hiking with a huge group of people. When I started out a few years ago I was the only one with a gravity filter - the ULA Amigo Pro. I got a lot of raised eyebrows with it. Everyone thought it was going to be slow. All the other hikers were busily getting down with the Sweetwaters, Hiker Pros, Varios and whatnot (never a Pocket, tho) - there were also the handful of holdouts with that good ol' First Need. I noticed a lot of times I was sitting and waiting for them after filtering. Lots of swearing when they dropped something in the water or broke a handle.

Now when the group goes backpacking, I see three or four gravity filters every time - Platy Cleanstreams and Katadyn Base Camps. All of them use the glass fiber type filter with activated charcoal in, like the Amigo Pro. Not a lot of difference in flow rate between them. I guess people really do need to see things to believe them.