I wouldn't say I have flawless skin, but it's "nice", I suppose.
It definitely depends on that look you're going for and the texture you want to give your skin. There are foundations for a completely matte look and then creamier, dewier foundations.
Also, I find it easier to blend powders and blushes with a little bit of foundation to serve as a base.
Foundation can be useful for more than just covering up imperfections.