I use foundation almost everyday, except of course when I'm having a lazy day at home. I think I look tons better with it on than without. I have these dark circles under my eyes which really do my head in, and because I'm naturally quite pale, the foundation I use (currently using Maybelline Dream Satin Liquid - Light Porcelain) gives me a bit more colour, evens out my skin and gives me a much healthier look.
I am careful not to overload and cake my face though, as many girls tend to do. That's not good at all. It looks awful and is bad for the skin. Also, getting the colour right is another thing. Orange faces are really, really not good. I make sure my face is clean before anything, apply a thin layer of moisturiser and then a thin layer of foundation - which I then set with a light dusting of power. Sorted.
I'm very happy with the foundation I'm using at the moment. I mean, it's never going to stay on ALL day long without rubbing off a teeny bit (despite what the adverts tell you), and it really blends well.. colour-wise and texture-wise. I used to be a L'Oreal girl, using True Match and Infallible - but I didn't get on with either of them.
Oh, the joys of being a woman.