Count me on the three-meals side of the question. I've tried mini-meals before, but they leave me feeling constantly semi-hungry and unsatisfied. Also, I prefer to have complete hot meals, with a meat and one or two hot veggies, and it's a lot harder to do that on mini-meals. I try really hard to avoid snacking in between meals, because I don't tend to actually eat less at the next meal as a result, so it's just extra calories. I'll occasionally have a snack to avoid going to the gym on an empty stomach, or if I'm up much more than six hours after dinner, but other than that I don't eat outside of mealtimes. My DH is a big grazer, and I think that's partly why I've actually lost faster than him -- he eats more nuts and snacky things than he realizes, then goes and has regular meals with me.

OTOH, note that I have a, shall we say, healthy appetite, and usually average 1800-2100 calories a day (and have done so all along while losing weight). A 500-calorie meal leaves me pleasantly satisfied instead of too full, so as you can imagine, 200-calorie meals don't get me very far. Maybe they work better for people with smaller apptetites than mine, who can't eat very much at a single sitting, but they're not my thing at all.