I was very impressed with the POR-15 shipping I received. It was prompt and accurate. It's quite the process and a bit costly but well worth it I think considering the reviews I've seen this stuff get.
About line-X - I am EXTREMELY impressed with Line-X, both the service & the product.
Also, a note back ot the POR-15 - I think the fact you have to order it is one way POR-15 can control their prices - as they have a monopoly on the sale of their own product. This allows them to maintain quality control as opposed to being pressured by retailers to lower prices which may cause them to skimp on quality. Just make sure you do the treatment right - you need to buy the marine clean degreaser, metal ready, and a can of the paint as it is a 3 step process to get the paint to adhere (4 step if you need to wire brush away some of the flaking rust before you marine clean it).