I agree that the FIRM packs a wallop into 45 minutes of working out - I'm guaranteed to get a full body weight workout (well, or almost, some tapes skim on the abs, back and/or chest in my opinion) *and* stay in my aerobic training zone for 50-75% of that tape.
When I first previewed FIRM Parts Upper Body (edited from the Classics), I was appalled by the dated outfits, the come-hither looks, the setting, everything! I traded that away in less than a heartbeat. Please bear in mind that it doesn't take a lot to keep my attention either, and I only ask that there be minimal whooping and silly outfits in my workout videos
This is coming from a person who really enjoys the low-key "PBS-like" production values of Francesca Gern's Weights III.
Then, a nice VFer convinced me that Tough Tape 2 was worth trying, so I took the plunge and even went out to my local hardware store to buy a Rubbermaid step-up box ($19.99, very sturdy, works great for household chores too). And amazingly, I *liked* it. I went on to collect a few more FIRMs - the ones I like are compact, newer, and focus on their version of "slow and heavy" lifting with some aerobic effects coming from all the standing legwork and short cardio bursts like Maximum Body Sculpting and Super Sculpting. I really like FIRM Strength too but it's an hour-long and I don't often have a full hour to work out on weekday mornings.
My beef with the FIRM is that you really can't have the best of both worlds with their tapes - I could never *safely* lift the amount of weight I do with Cathe while using a FIRM tape. There is no way I could ever hoist 25 lbs over my head in a military press at the FIRM's pace! Nor could I curl 30 lbs with the FIRM, but no problem-o with Cathe's Pure Strength series. And I can a way more intense, continuous cardio workout by jumping on my bike and popping in any spinning tape.
Recently, I began collecting some Classics and now that I've seen them in their full form (instead of an edited Parts tape), I am more keen on them. I haven't actually tried them though because I am rehabilitating my right knee and the lower body moves in Vol 1, Vol 2 and Vol 4 are way too fast or require kneeling... both no-nos in the short-term. I do think that Vol 2 looks like it will overwork the shoulder muscles, in particular the very sensitive rotator cuff (I have the same complaint with Karen Voight's Great Weighted Workout's upper body section). Ouch.