Well, that's about what a Leslie Sansone walking workout is: marching in place, kicks, knee raises, kick backs, side steps.
If you're sweating and breathing hard, I'd say it's a good workout, but the only way to be sure is to check your heart rate and make sure you're in the zone for fat burning.
Do a google search and you should find the calculation to figure it out.
A heart rate monitor is a neat toy to have and it can tell you your heart rate during exercise and how many calories you burned.
There's some debate about how long you should do cardio. I *personally* have decided to not do over 30 minutes. The amount of calories burned is negligible (sp?), and to me it becomes boring after 30 minutes.
Good luck to you