P90X is awesome! We started it last year and did the program for 90 days. I went from 212lbs to my 155lb goal. I did not change my eating habits although I did replace my Diet Mt Dew for water. The program is insane if you aren't in shape and I wasn't. We started off slow and worked our way through the DVDs.
After meeting the love of my life and settling into family life I began gaining some weight back. 30lbs to be exact....she's an awesome cook! We just got the
10 Minute Workout DVDs by Tony Horton. These are much easier than P90X but still kick your azz! We haven't totally committed ourselves to these yet but once we do I know they will work! Tony Horton has the muscle confusion down packed!
Good luck with whatever workout you decide on. Remember to start slow and work your way into the full workout!