I made one a few weeks ago and I use it as another variation in my jelq routine. So far I find that it is able to dig into the base of the penis more efficiently than manual, so that is a plus. That being said I think there would be a limit to how far down you can dig it in as I'm getting close to 9" long and I find that my hands and the top of the device are hitting the top of my glans when I begin my stroke so you won't get a review from someone like DLD on it. I find that it is very intense and I have to mind my erection level, too hard is not good where as manual I can adjust my grip until erection level goes down (I know many do this here). Pressure from jelq device is primarily applied to the top and bottom and expansion is only to the sides of the penis. I will keep using it, again only to compliment my manual jelqing not replace. I know Goldmember has trialed it for a month and is not impressed with it at all however everyone is different. If you want to make one search "Jar Lifter".
It's a different feeling with the PJ. Pressure is applied to the top and bottom of the shaft and it can be very intense. You have to be carefull with it, because of the nerves and veins in the top of the shaft. Some have managed to use it sideways (rollers on the sides) but I found it very uncomfortable and not possible unless I hold from the glans with my other hand, to prevent twisting.
It doesn't replace manual jelquing IMO, but it is a good device to mix into your routine, and specially handy when you have no time for a full Penis Enlargement session.