I stumbled across this site yesterday.  It has photos of some familiar and reviewed providers mixed in with the usual array of fakes and scam artists.  It's also difficult to tell whether the services for some providers are a la carte or prix fixe.  Has anyone had experience finding legit ladies on this website?

Looks like they scraped these from other sites. I highly doubt providers even know they are listed here and I bet some (many?) have services listed they don't really offer.  

So what is UI?

The user interface.