My family and I just bought an eliptical?

(and changed a great deal in our diet) because we are trying to get into shape/maintain a healthy life style for life. I've only used it for 4 days so far, but I feel great. I go on 30 min. a day and burn about 400 calories (steadily increasing how fast I pedal). But my question is how do you guys feel about elipticals? Have they helped you get into shape, should I see effects if I keep up my 30 min. a day...and how fast are results typically seen? My goal is to lose 15 pounds by the time I go back to school in September.