Ever used one? There are some very attractive silicone molds coming out just in time for holiday baking. I especially like the shapes of some of the silicone bundt pans, and they are a LOT cheaper than their cast metal counterparts. BUT... Do they work well? I'm wondering whether they're so much cheaper because they're only good for one or two bakings. I'm also wondering if the large (12 cup) molds hold their shape once they're filled with batter. I'm also assuming that the way to go for baking is to set them on a cookie sheet, or even inside a layer cake pan, then fill them, move them into the oven and bake. Do those of you who have used them love them or hate them? A curious mind here, and all that jazz... Thanks!