I think that Luther has done a very good job of objectively pointing out the features of the Volcano that make it attractive. I understand the backlash from some users against the Volcano Snobs, though I haven't seen much evidence of that on this site (not that I've been here long).
The biggest "con" against the Volcano is the cost, compared to other vaporizers. As hmmurdock points out, a vaporizer (probably any vaporizer) is going to make your use of herb more efficient, which makes for a pretty quick return on investment (less than 2 months for me, I think). I tend to pack my chamber about half full in my Volcano, a bit more than most put in there. Despite that, I am getting a huge efficiency boost, especially when you consider making edibles from the duff.
One way of dealing with the cost is buying a used one from eBay. I got one (classic & solid valve) for $300 shipped almost a year ago, and it's been great. Looking now, it seems that they're selling between $300-400, which I would gladly pay again if mine were to die.
