I bought a scale... it's really useful to have one for measuring stuff like flour and pasta. Most scales also allow you to convert between grams and oz. Since all of my measuring cups are US measures, I also use it to measure things for European recipes (eg. 200 gm butter). If you're going to cook a lot, and use recipes that aren't just from the US, it's definitely a worthwhile purchase.

About the volume measurement... if I remember this correctly, one gm of water is one ml or one cubic centimter of water at room temperature. Or something like that.....