I did it for 3 years before I got pregnant with DD and I don't think I'd have got pg without losing all that weight - in total I lost 4 stone and went from a lumpy size 16 to a very shapely size 10. I was full of energy, my skin was fantastic and I didn't have that horrible drawn look that peeps who lose a lot of weight tend to get on low-fat diets spits.
People who say it's unhealthy either haven't read the book properly (it's amazing how many peeps don't bother to read the research and the reasoning behind something and just dive straight into the diet, then complain when it doesn't work properly or they feel ill) or just haven't read it at all and have believed the scare stories in the media.
It's not just eating meat, I ate more green veg on that diet than any other time in my life! I had to have an emergency c-section and the doctors and midwives were very impressed with my blood counts and blood pressure - not something that would have happened had I been living on baked potatoes and beans on toast like I used to!
There is a support website which is really, really helpful and informative, here and I found it a lifeline while I was doing it.
Unfortunately I stopped doing it while I was pg as I didn't want to take any risks (we'd been trying 10 years to conceive), consequently the weight piled on and 2 years later I'm still trying to get motivated enough to get back on it - it's a lot of hard work preparing all your food from scratch!
And that's probably the biggest downside - the intensive cookery - the whole point of Atkins (which sadly his company ignored) is that you eat 'proper' food without the processing, the artificial additives, transfats etc that give you health problems. And doing that with a 2 year old is almost impossible! I'm waiting for her to get a bit less demanding before I go back to it....