I am seeing a definite trend here and it looks like -- all of the above. I think one problem is that your sample is biased by including only people who are interested in reading enough to be active in an online message board.
I do use free books to get me into series. I also follow authors I like, and recommendations of others. I also rely heavily on Amazon's lists of recommended purchases.
In terms of purchasing, I am quite comfortable with buying indies, but I usually look for some sign of validation before diving in, typically something like an average rating in the four star plus range, and the more reviews the better -- one to five reviews isn't enough.