It's a good device, but it's mainly useful for increasing the intensity of your jelqs. For that reason, it's not for beginners. It's also fairly expensive. You can, however, make your own (there is an article at Thunder's which gives information on how to make a jelq device).
I have this device as well and it works pretty good. Try not to use too much pressure and try to trim the pubic area. Because least for my it catches sometimes and OUCH. I bought mine about 3yrs ago or so and only had to replace the rollers once. But I don't do too much PE anymore even thou I need to if I ever want to make my girth goal.
Just a small update on this topic. I said the replacement rollers cost some decent $$ I wasn't lying. When I emailed them they told me it would cost $37 (shipping is in there) to send me some of those rollers (2ea to be exact). That is just crazy the actual full device just costs $20 more. How can 2 rollers with padding cost that much.
workinit: Devices aren't necessary, but they're useful when you are looking to increase the intensity or to give your hands a break. The jelq device could probably be used after the beginning routine, maybe later, depending on your PIs.
I bought one for $99.00, that was the cheapest I could find it. I would say hold off for at least 3 months before using it, like Remek said it is really only useful in increasing intensity which is something that should be done after the 3 month "penis boot-camp" phase.