I hope that makes sense. Now for the other questions...

The only smell from it would be on your breath
You can tell that something is in there, even though it's not smoke
Deffinetly worth it :thumbsup:
If you smoked the same amount in a joint, that you would vaporise in this, yes, higher than a joint.
The only dangers is that theres peices of glass remaining in there when you smoke out of it, or that their's chemicals on the lightbulb