I certainly wouldn't agree that all vlcds are unhealthy. CD/LL/LT have been formulated to provide the body with 100% rda of all the vitamins, nutrients, etc that it needs, so are actually often a healthier way to 'eat' than most of us ate before the diet! Slimfast however is designed to be used as a supplement to healthy eating, as it doesn't provide the body with everything it needs. If it were a complete meal replacement vlcd then it wouldn't be allowed to be sold in shops. Naturally it's your choice however, as long as you're well informed of the risks that following a vlcd that isn't nutritionally complete can bring.
Also, Slimfast isn't low-carb, so I imagine you're very hungry!
Jot: I assume you're on 4 tetras a day if it's costing you that much?
Jo x