I love this too. I don't use this exclusively, I use halo, LG BNB Fair, and BE too but I always carry my philosophy as my retouch make up. It's a bit more matt than the others so good for fixing shine and adding a bit extra coverage. It's the one I take on holiday too as it's so easy to use and carry. You can also open it up and use a brush, the baby kabukis are a perfect size, but that can be a little messy if you're not careful.
As for colour, I use the natural. I have milky white skin so use the lightest in everything: smashbox F0 in healthy fx, fair in halo, fair/fairly light in BE. If you have a bit more colour about you then I'd reckon that beige would be better. There isn't a huge difference in the shades, they are quite forgiving, but natural may be a little pasty on more medium toned skin.