I don't use the family trees at all; I consider them the equivalent of the Ancestry trees - good for suggestions of where to look, but everything has to be checked and sourced - lots and lots of people put into the wrong families,bad dates, etc. My favorite was the guy who was born in Schenectady NY in the 1500s, when there was no Schenectady, and not many white women living in the area. Unfortunately, Ancestry has some sources that I can't find on Family Search.
Findagrave is also a toss-up. It's great if you already have your sources and it backs them up, and for suggestions on where to look, but it seems that the family information, when it's there, is not reliable.I do like the ability to search for other family members in that cemetery, or in that area.