I started the first or second week the streaming started, so late December 2014.
Almost exclusively. I prefer walking on the treadmill for my cardio. When cardio was included in the main workout I did it, but with lots of marching in place. Now that it is separate I stick with the walking. I walk after every workout, mostly to convince my legs that they can still move
I do stretch thoroughly as well.
This last week I decided to add in Hamelin. I have read good things about his method. Tracy improved my arms a lot but I decided to add in Hamelin's Armatics and see if I can get stronger and even more toned. After my arm experiment I might try his ab workouts. If I want to change my abs/core I am going to need more than the smattering of abs in Tracy's workouts. One thing I found, is that even after Hamelin fries my arms I still want to Tracy's arms - they are just fun.
ETA: The frequency of my workouts has varied a lot over the last year. When I started I was working out irregularly. Tracy was a good choice for me because the fresh weekly workouts kept me interested and just guilty enough to want to exercise. Now that I am stronger and been doing it a while I am able to be workout more regularly and I hope to keep that up.