A co-worker of mine is planning on trying the Dr. Bernstein diet after hearing positive things about it from other people. That's not much help, I know.
The thing about diet plans is this - they all work. I came to this startling insight after going on one for the first time in my life last year (I used L.A. Weight Loss). A long story short - I suddenly realized I was over 50 pounds heavier than I was in 1998, when I found out I was pregnant with my first child. I followed LA's plan to the letter, and was very successful - I surpassed my goal weight and am able to fit into most of my old clothes from 10 years ago. My success wasn't due to LA's magical weight loss formula (I also re-started my old exercise regimen). It's because I changed my eating habits back to healthy ones and got up off the couch.
Basically - if you want to follow a weight-loss program, any one of them will do if you embrace the idea of changing your lifestyle. Jenny Craig is very expensive as you have to buy their food, but I know a woman who lost 70 lbs on it and has maintained her weight loss for over a year now while discontinuing use of their products. I know others who have had a lot of success with Weight Watchers. From my own observations - people who complain that programs "don't work" are the ones that don't follow them or drop out after a couple of weeks. The staff at LA told me that the vast majority of their clients didn't last past six weeks of the program. Of course there are people who like yourself, misskitty, who may be taking medications that affect their weight or that suffer from other health issues, but I think most that aren't successful are looking for a magic cure and get impatient when they realize that it's far more work to take off excess weight than it is to put it on.
ETA: I re-read the last paragraph and I think I sound harsher than I mean to. I researched weight-loss plans online before I chose LA, and I found many, many complaints about them and other programs - "It's a rip-off, it doesn't work"; "They forced me to buy their products"; "I don't have time to attend meetings/get weighed-in three times a week"; etc., etc. What convinced me to use a program was one person's comment, who said basically the same thing I said above - if you follow the plan correctly, then it works. If you don't, then it doesn't.