Just quickly skimmed Leo. Counted 80 ads (not including dublicates), and about 30 are confirmed real. So that gives us 37.5%. But this can change depending on who posts, who is traveling in town, etc. So lets round it up and say on any given day, looking at the ads, about 40% are real and it is not that difficult to tell the difference (though every once in a while you need to actually message them or get scammed to truly find out, so yes there are time that its not that simple. But you'll get the hang of it).
As for whether or not that 40% is GOOD service, that's an entirely other debate