I got my Ray Flash recently. I like it. I think it's a nice tool to have some fun.
I've posted my detailed review:
Ray Flash ring flash adapterThe build quality is good. The light loss is just a stop.
It's been discussed, however, that it puts some stress on flash head. I wonder if there are any long time users of this light modifier that can confirm that it does not cause any problems with flash head (any damage?). To me it seems that it's not that heavy, but a pound of plastic hanging on a flash head... I guess only time will tell...