Thanks for the welcome!
Caitlin, , I love BFBM (Jillian Michaels' s 'Banish Fat Boost Metabolism, ' available on YouTube)! I think the slightly slower, more controlled pace of, say, Circuit 6 is what makes it such a killer. Jillian and her crew always have such fantastic form- unlike, say, JNL or all of Shaun T's vids. So you really learn how to get maximum effect from the moves with her, IMHO.
Lavender, the core stuff is hard to crack but it is important and if you can get in the habit of keeping everything tuckedin, it will sort of start to stay that way all the time (like a dancer ).
Yum, I love Zuzka. She seems very sweet and likeable, which helps me get through her workouts. I love herZCut cardio, specially the second one, which has you do four high knees and then a plank... 60 times in a row!
I like her yoga vids, too, because they are short. One of the reasons I never got p90x were the dark rumours about a 90-minute yoga video! 
Will add my impressions of BodyShred when I get home from work.
It is so NICE to have people to talk about these things with.
Does anyone else like that bit from Tabata Power (Insanity Max 30) where he steals that woman's water bottle and she just radiates rage?