I really like Mindy's Cardio Toolbox. It has a lot of variety and is very easy to mix and match. The choreography is not complex, but the intensity is up there.
I LOVE Christi's Fabulous 4. I love complex choreography, but it took me a while to pick up the second portion of Step Heaven. Once you learn it is a lot of fun. Still Steppin is a fave of mine too. The hi/lo is fun, but i'm just not a huge fan of hi/lo in general.
Aila