Will Jillian Michaels DVD's help me?

I ordered 2 Jillian Michaels DVD's- 30 Day Shred and Yoga Meltdown. Should I alternate between the DVD's? Like do the Shred one day and Yoga the next or will I ruin the effect of each DVD? I'm already dieting and have lost 10 pounds but have 15 to go. Have you used either of these DVD's? Do you know anyone who had really good results with them?