If you're talking about a ring flash mod for a speedlite... yea, not fond of them. You'll have to be exceptionally close to your subject to get anything to look like a true ring flash. For the price (Chinese knock-off's) they are worth a try but if you're really looking for a ring flash, only the real deal will work. I've used Orbis and some knock offs but eventually ponied up for the dedicated strobes. Currently I use Elinchrom's Ranger and Quadra ring flashes and they perform flawlessly.
You can check through my site... there are a few portraits taken with the orbis. Ring flashes are a specialized look (or macro work), glammy, flat lighting... not really the best for general portraiture. I use Lastolite Ezyboxes much more frequently for speedlite portraiture.