I have always loved miniatures, even when they were just used in a very abstract way (show general marching order, show how many opponents you have left, etc.). Sadly, I am allergic to some of the VOCs used in most paints. This means that most of my metal minis stay unpainted. Unless, of course, a friend offers to take them home and paint them.
Prepainted minis are a great boon to me, as you can imagine. I do not have to paint anything and I get colorful figures to use. I was not overly thrilled with the random packaging of the DDM figures, but sometimes you have to take the good with the bad. I did some purchasing of individual minis, but I think people tend to charge way to much for them. I have bought a number of the Reaper Legendary Encounters minis, and enjoy the non-random nature of them.
Now, to finally answer the question. Prepainted minis got me to buy more minis then I would have without them. I do not play the DDM game, but I do enjoy seeing a lot of miniatures spread over a table in an epic battle. If I could get more prepainted minis for a reasonable price, and of types I want/could use, then I would be happy.
Oh, I almost forgot. When I was employed I was starting to buy more metal minis and shying away from the prepainted ones. I then just bribed people to paint them for me in a timely manner. It worked, and it got both me and the painter something we wanted.