My sister did lighter life and was extremely successful on it. I think it depends very much on where you are in life and how committed you are. She certainly didn't crave nutella (which she did before she started!) but after a week or two of soup all she wanted was a nice crunchy carrot or crisp apple!
It's not easy. There are a lot of people who drop out. The key to keeping weight off seems to be the management programme afterwards (counselling and accountability).
She also says it seems to make a big difference who the counsellor is (some groups appear to be much more successful than others) so check out real people in your area who have done it before you pay out for it.
I wouldn't say it was dangerous (sis was monitored by GP with blood tests etc... every couple of weeks) and TBH, the packs are so vitamin rich that her hair got shinier, thicker, eczema cleared up and asthma improved. In fact, there are loads of stories of people who are 'infertile' suddenly becoming pregnant whilst using light life!
There is a negative side though. My sister lost 4 stone (and has kept it off) but she is still not happy with her body. Losing weight won't tighten up your skin and her GP has told her that they only way to get the rest of the weight off (another 1/2 stone or so) would be surgery, as it's not fat, it's excess skin. This is not available on the NHS and would be very expensive if she decided to go for it.
The fact is, if you are very obese and need to lose weight for health reasons, it will work (if you are committed), but you may not end up looking like the sculpted model you hoped too.