I wasn't convinced before, either, but now that the prices are dropping, there will hopefully be more people in the databases.
Of course, the effectiveness of any research tool will vary from individual to individual, and (just like all the other things that we genealogists spend our money on) we don't know how effective any research tool will be until we've bought it. I'm sure I'm not the only one who has signed up to a paysite, only to find there's little of interest on it ?
My own genealogy wall concerns people with my family name in (what was) a small village on the outskirts of London. I know that one of these namesakes was my g.g. grandfather, but I have found no way of telling whether any of the others with the same name were related or not, and I don't know where the family originated. Since I have made contact with the descendent of one of these other people, I'm hoping to persuade them to take a DNA test, to be able to establish family relationships (if any), and maybe even an origin for the family.