I was OK with mine--not great for strapping on early and watching tv as has been suggested to me, blocks your eyes a bit--but it feels ok for me and air flow is not an issue. It's diffuse and blows away from you no matter what position you are in.
My problem has been leaks. It doesn't leak until I relax completely. This took me awhile to figure out, but when I relax my jaw drops and suddenly what fit fine when I first lay down doesn't anymore. Even the fit test with the machine says it's leaking. Leaks around both sides of my lower mouth or up on my upper cheeks. Only way to avoid that seems to be to strap the thing on so tight it is not comfortable. Could well just be a liner or whatever they call the soft plastic piece issue, but to figure that out with the DME provider is more trouble than its worth.