JWTG,
I do not have any experience with Insanity, though have heard good things.
P90X has more of a proven track record, which is why I tried it. If you do as the guide outlines, the results will follow.
I used to be 220 lbs (@ 5'10"). I have always been a great runner and had a strong lower body but lacked in upper body strength. I lost 50 lbs just on nutrition and running on my pursuit to get fit for the CF but felt I could do more. I decided to give P90X a try as I already had a chin-up bar, select tech weights and push up bars. I have just started the last phase of P90X this week and can honestly say I am in the best shape of my life. While the weight loss has been minimal, that is not an accurate gauge of P90's effectiveness. My muscle mass has significantly increased (hence minimal weight loss) and my BF% has dropped almost 5%. I am now 164 lbs and 14% BF.
As to your problem of low ceilings and no room for a chin-up bar, it's not as big deal as you think. I rent out the upper half of my house and reside in the bottom half (don't need all the room for just my wife and myself) and have low ceilings and few doorways. On the workouts where you need the bar, I simply pause the DVD, walk about 30 feet to the bar hanging in my bedroom doorway, perform the exercise and return to the living room. It's a nice quick break if anything. As for low ceilings, I'm 5'10 and just miss the ceiling with my weights above my head. You could also use the bands and save more room. In Plyometrics, you won't be jumping to the ceiling to often (unless you want to burn out early)
I think any workout routine performed everyday will net you results, however, it is a fantastic stepping stone for people who don't know where to begin and once you are done the 90 days you can restart the program or take what you have learned and make your own routines. Remember, muscle confusion will keep you from hitting a plateau. Another good piece of advice is 'nutrition'. This may be as important, if not more important, than the exercises themselves. I don't use the recipes included with P90 but I follow their guidelines (IE 40/40/20 carb/pro/fat intake) and have tons of energy and fat loss.
I plan on making my own routine after the conclusion of the program but am completely satisfied with my decision to do it. It is not easy but rewarding. I now feel more than ready should an offer come my way soon and I am off to BMQ.
My :2c: