I've entered a few of them. Most of my prizes were won during meetings/community events or through community interviews. I've won a book, an Icicles dildo, a bottle of massage oil, and...I think that's it.
I feel like I don't have a good chance at winning so I only do it for the ones I'm really interested in that way I know I've given it a shot. I don't want to add my name to the list for things someone else might really want.