Here is my limited experience with this tool (also tried the one for Bowens flashs).
It is quite large and unwealdy, and you really need to be on a tripod to use this for long periods of time. The ring is too big to use as a macro ring flash (IMHO), and you would be better off with a deticated macro flash.
For portrait use the adaptors create too soft a light to be used in the normal ring light situations (fashion and music portraits), but still has the ring light shadow problems that makes it not well suited to portrait situations. So while this is a cheap way to get a ring flash, you are actually not getting a ring flash (if you know what I mean). Not worth it for this amount of money (IMHO).