The elliptical is a great piece of equipment for gym-goers with physical limitations.
For anyone else, I'm not a fan of the machine. Not only is it one of the most boring pieces of equipment in the gym, it can also be extremely ineffective.
First off, the elliptical doesn't use a natural body motion to work your body. Workouts that use natural motions like running, bending or jumping are much more effective at toning muscles. Sure, the gliding motion of the elliptical burns calories, but that's about it.
It's also easy to slack off on the elliptical. With the treadmill, you at least have to keep up with the pace you set. On the elliptical, you start off with guns blazing, and 10 minutes later you're crawling along like a turtle.
You're much better off doing a 20-minute cross training circuit (burpees, jumping rope, jumping squats, etc.) than 45 minutes of slogging along on the elliptical. If you're looking for another low impact exercise, try the rowing machine. This will get your heart rate up, and also work your upper body and back.