I have. Since I've never had any problems the, only way to tell how well it performs would be to cut one open after use and compare. So sometimes when I buy oil (I use their oil) I get a couple. Gonna try their chain lube this time and see if it comes close to my favorite blue can
i've used them before. as said above.. i didn't take the time to actually inspect the contents during the change. I do know however that on my exhaust setup now.. the lower profile Amz filter fits without any other hassle. To me its worth a couple extra bucks.
I would use them as I use Amsoil anyway, but I love the ability to use the welded nut on the end of the K&N. I changed my oil this past weekend in about 15 minutes and could not be happier with the process as it stands.