Ellipticals have really added another dimension to exercising by offering a totally non impact way to exercise because your foot never leaves the surface of the footplate. Easy on the joints especially if you have been a runner for a number of years and your knees have taken a pounding.
Most ellipticals have incorporated handles that move back and forth engaging the upper body muscles as well - arms, upper back, shoulders and obliques. This really helps ramp up the heart rate.
Almost every manufacturer is making a line of ellipticals. Most tend to be quite large so you do need ample floor space and head room.