I have a similar one from ebay, for my canon system. Mine either lights up 360 or 180 degrees. It's not a flash but basically just an LED lamp (like a petzl only round). Pretty bright, and was useful to have around last week during a power failure. It does help light up the subject when using a macro lens but I find it limiting in terms of it not being adjustable or positionable to try to reduce shadows. But, there are other options for that.
Used for macro work, they should be fine. Used in lieu of the large ringflashes often used for non-macro work, they would leave odd catchlights visible in the eyes of those whose portraits were taken with this.
They don't appear to be a full ring. I don't know what your intended use is. If purchasing be sure it will fit your lens. You might also consider a bracket from Bogen/Manfrotto that you can attach two conventional flash units many available or that you may already have. The bracket can be adjusted to have the flashes at 45 degrees or pretty much any angle. Each flash can be set at whatever power you want. You would need a PC cable that attaches both or a peanut slave for one. Shadowless light especially if glass or reflective subjects are involved and the flash unit(s) can be used without the bracket for other types of images.
It doesn't look as well made as an Orbis but its also MUCH cheaper than the Orbis. http://www.youtube.com/watch?v=wvKcSDsTpvI
I have been wanting to add something like this to my kit for a while but just can't justify the $175 for the orbis system. If you decide to get this, please report back on how it works.