I've used inferior elastic cords that stretch under use, and that includes some of the inexpensive cargo nets that sag out of shape and lose their elasticity.
I bought a set of "bungee" branded cords at a Price Club in the states that I still have and use, with only one failure when I kicked it off the passenger peg mount with my foot on a very long and boring ride.
I picked up a set of Rok straps at the December show and will try them out this May on a four day trip to Virginia and back.
I still carry a bit of 1/4 inch braided cord, enough to lash the load onto the bike if need be. It packs into a size smaller than my fist and is good insurance imho. I tend to loan it out to other riders that rely on inferior straps.
Those ratchet and cam buckle straps? If you are okay with crushing your gear down, and don't mind that a load shift might cause and end to fly off, then you'll probably be okay. I don't care to use them on the bike, but I here that they work great at pulling a stuck bike out of a mudhole or hanging it from a tree to remove rims for patch repairs.
I like to be able to take a wee jump or two on my fugly bike knowing that my gear is still there, so I use two bungee cords criss crossed, and one on either side of my load as insurance. Later on I'll stuff a rain jacket or a water bottle under them between stops. It works for me. The rok straps have loop ends, so they stay on the bike when you unclip the buckles. They look really serious and as if the buckles and elastic will hold up to my redneck abuse.
