OP, I been there myself, a lot of flat finishes have been done and I was looking at doing a flat white myself, but then did a bit more research and found out a few things. The main reason I didn't do flat white was because I found out it takes a lot of money to get a flat paint job done right, even mediocre jobs often look discolored (on flat black for example some spots would appear darker)
and another thing was I wanted to do something different than the flat everyone was doing, I went Satin White, a semi gloss was used, and it's the perfect balance between flat and gloss. I don't regret it, because I love it and I don't get any flack from my boys for being a "matte" poser. Everyone seems to appreciate the originality, so yea my suggestion would be unless you have 10 g's or more to spend don't go with flat. I'm sure a lot of guys here will jump in and disagree with me, but I know from personal experience I'm not just stating an opinion.
here's some pics of an expensive Flat White paint job
and here's a Lambo where I got my inspiration from, the color comes like this from the factory, it is matte but under the lighting in the second picture it looks almost satin, and that's where I got my idea to do my car satin white.