Yes, it is expensive, but there are offers available - saw one on TV shopping channel, and probably more on-line if you have a good look.
We've had one five years or so. I don't think an ordinary blender would survive long doing things the Vitamix does - particularly making ice cream from frozen fruit, or crushing ice for smoothies.
We don't use ours as much as the shopping channel suggests, as they say you'll use it every day! But it's good to have available; we also do soups, but haven't 'cooked' in it, which in theory is possible if you run it for long enough, and the contents gets hot.
Comes with good cookbooks and advice, and a DVD I think. Depends how keen a cook you are, how much you'll use it. Easy to clean, bit of hot water in bottom, drop of Fairy Liquid, and run it for a few minutes, then rinse it out.
If you can afford it, I think it gives you scope to do things not easily achieved with lesser machines.