I'm not a BodyRock moderator or anything, but I can tell you that when I started doing BodyRock several years ago, simply doing a 12min workout all-out every day, and cleaning up my diet was enough to start seeing results within about a week. Co-workers were making comments within about 2 or 3 weeks. So if you're doing a 12min HIIT workout AND lifting weights, I bet you'll see results quite soon!
Once I got pretty darn fit, to start seeing even more results, I did Lisa Marie's 30 Day Real Time challenge (when she was first doing and uploading it!) which you can get now in Sweatflix. Those workouts will kick your bum HARD, but I saw crazy results FAST! I think for a newcomer it might be a little overwhelming and not necessary (Catching Fire is great!), but if you're already a fit chick, then it will get you more fit pretty darn quick.