Is a "gazelle" type of elliptical beneficial exercise?

I have a Weslo Easy Stride (imitation/wanna be Tony Little Gazelle)..is using this elliptical thing beneficial? Am I actually getting exercise from using it? It feels like it's doing something, i.e. sore muscles first few times, increased pulse. I'm building up the length of time I'm on it..started with 15 minutes and now up to 30 minutes.