There are two types of vaporizers. The first is the conduction type vaporizes the bud in a heated metal bowl(usually covered by a glass dome) . The second type is the convection type where hot air is pulled through the bud when you hit it.

I have owned both types and the 2nd, convection, type is much, much better. The first one I had was the BC Vaporizer and it was a piece of shit. Well, maybe that's a bit harsh. It did get me high but it seemed like it wasted a lot and I had to use a lot of bud, much more than just smoking it. I literally ended up throwing it away.

The second vaporizer, and the one I use now, is the Aromazap($100 delivered). www.aromazap.com This one is a convection type and is awesome. I only use a tiny amount of bud and one or two hits gets me really high. Of course a lot will depend on the quality of your bud. If you only have shwagg don't expect miracles.

The only problems I have with the aromazap is that it takes about 30~45 minutes to heat up. Not a huge problem but not too convenient. It can also get kind of hot on your lips. If I had to do it again I would probably go for a vapor brothers ($150) http://www.vaporwarehouse.com/store/shop.php?p=vb.html they heat up in 5-10 minutes and have a long whip to help cool things down.

Of course the volcano is supposed to be the ultimate vap but a little too pricey for me. But, if you've got that king of cash its supposed to be the way to go