Cardio Equipment

Hello!  Yesterday morning I was doing cardio and thought to myself, wow this can be sooo boring.  There are a lot of good machines to use, but when you do cardio a few times a week they can get monotonous.  I try to mix it up a little bit and use the rowing machine as part of my cardio workout.  I like it because not only does it work your lower body, like all the other cardio machines, but you also get a good upper body workout.  Have you ever tried this as an alternative to the typical cardio machines?  What's your opinion on the calibar of workout you get as compared to the treadmill, elyptical, etc.?