I have a policy: when I need to use oil I use oil. I don't skim off the top with the latest fat-reducing miracle. I use real butter and olive oil in almost all my cooking and I still maintain a healthy weight and an active lifestyle. My grandmother has gone to eating margerine and using it in baking and cooking, which I think is a horrible offense against taste, but my grandfather has gone back to using butter in almost all his own baking because I re-educated him on how much better things can taste if you just do it the way it should be done. :)
I know there are a lot of people for whom this isn't an option. The low fat diet is a must for health reasons. I do feel, however, that if you're making a dish that calls for butter, use butter. Just don't eat that dish all the time. Moderation, and a healthy dose of taking that flight of stairs instead of the elevator, is the key to a healthy life.
And this is coming from someone who does believe in the benefits of organic farming and pure cooking. Yes, this is basically a rehash of what Mark said, but it's also one of my pet peeves. Synthetic oils and fats are, in the most part, worse for you than their natural counterparts mostly because of how new they are. Yes, they've been tested, but who knows what effects they could have years down the line? Live and learn. It's kind of like Teflon, I suppose. It was supposed to be safe way back when it was brought into the cooking world, but there are studies now linking it to cancer. I prefer the time-tested, natural ingredients to new-and-improved chemical experiments. It's why I'm throwing out all my grandmother's old nonstick pans in 5 months and replacing them with a set of Emerilware stainless steel and cast iron. It's why I use butter in things that call for oleo. It's why olive oil is the top of my list of cooking oils. (I swear to you that I do not and will not cook like Rachael Ray. She scares me sometimes.) Some wisdom that came from my great grandmother may have been a bit dated, but her cooking advice is not. Pie crust is made with lard. Cookies are made with butter and real vanilla. If a recipe calls for buttermilk, use it. Cast iron can cook almost anything. Good gravy does not need to be strained of all the little flavorful bits; those really don't count as lumps.
But yeah, I've spouted enough myself. I can do that sometimes. :bounce: