Anything that gets you exercising should be worth looking over. I don't use the program, but I've heard nothing but good. I have heard they are tough. Definitely, if you get the spinervals, try and organize the tapes so that you can build progression and difficulty, rather than going full on all the time. Going full on will not do much for you as taking the time to adapt to progressive load on the body over time.
I've got a couple of the DVDs I use with my indoor trainer in the winter. My local university that used to offer a free spin class now charges a fee, albeit small, so I purchased my own trainer. The Spinervals sessions are rated for difficulty and I can tell you first hand that the two I have (rated >9 on a scale of 9/10) definitely kicked my butt until I got used to them. If you do consider them, try more than one (to avoid burning out). I've had no luck finding these anywhere to rent so I had to buy them. I based my choices on reviews at roadbikereview.com. Make sure you have a fan and something to drink. Also, I wrap a dishtowel around my head (it's soaked when I'm through). BTW, I have 1.0 No Slackers Allowed and 3.0 Suffer-O-Rama.