I've done 14 consecutive days and wanted to do a 30-day one, but travel/seeing old friends/family events got in the way.
Basically, you need to do it and pretty much forget having any kind of social life for awhile
After the initial 72 hours though, you will definitely feel more aware, sharp, energetic.
Most people who bash water fasting (aside from not understanding it) give up in the first 72 hours so all they get are the negative effects and never hit the positive period benefits.
Very important NOT to exercise with any intensity or you will simply burn muscle (breaking down muscle = fast fuel, ketosis - burning of stored fat for fuel = slow process).
I truly believe it can definitely heal many forms of disease, since your body has 100% of its energy for healing and wastes none on the ultra-heavy digestion process.
I think it can only be dangerous if you have specific genetic conditions, OR are at an already very low percentage of body fat.